cpython/Doc/reference/datamodel.rst

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.. _datamodel:
**********
Data model
**********
.. _objects:
Objects, values and types
=========================
.. index::
single: object
single: data
:dfn:`Objects` are Python's abstraction for data. All data in a Python program
is represented by objects or by relations between objects. (In a sense, and in
conformance to Von Neumann's model of a "stored program computer", code is also
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represented by objects.)
.. index::
builtin: id
builtin: type
single: identity of an object
single: value of an object
single: type of an object
single: mutable object
single: immutable object
.. XXX it *is* now possible in some cases to change an object's
type, under certain controlled conditions
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Every object has an identity, a type and a value. An object's *identity* never
changes once it has been created; you may think of it as the object's address in
memory. The ':keyword:`is`' operator compares the identity of two objects; the
:func:`id` function returns an integer representing its identity.
.. impl-detail::
For CPython, ``id(x)`` is the memory address where ``x`` is stored.
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An object's type determines the operations that the object supports (e.g., "does
it have a length?") and also defines the possible values for objects of that
type. The :func:`type` function returns an object's type (which is an object
itself). Like its identity, an object's :dfn:`type` is also unchangeable.
[#]_
The *value* of some objects can change. Objects whose value can
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change are said to be *mutable*; objects whose value is unchangeable once they
are created are called *immutable*. (The value of an immutable container object
that contains a reference to a mutable object can change when the latter's value
is changed; however the container is still considered immutable, because the
collection of objects it contains cannot be changed. So, immutability is not
strictly the same as having an unchangeable value, it is more subtle.) An
object's mutability is determined by its type; for instance, numbers, strings
and tuples are immutable, while dictionaries and lists are mutable.
.. index::
single: garbage collection
single: reference counting
single: unreachable object
Objects are never explicitly destroyed; however, when they become unreachable
they may be garbage-collected. An implementation is allowed to postpone garbage
collection or omit it altogether --- it is a matter of implementation quality
how garbage collection is implemented, as long as no objects are collected that
Merged revisions 75365,75394,75402-75403,75418,75459,75484,75592-75596,75600,75602-75607,75610-75613,75616-75617,75623,75627,75640,75647,75696,75795 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r75365 | georg.brandl | 2009-10-11 22:16:16 +0200 (So, 11 Okt 2009) | 1 line Fix broken links found by "make linkcheck". scipy.org seems to be done right now, so I could not verify links going there. ........ r75394 | georg.brandl | 2009-10-13 20:10:59 +0200 (Di, 13 Okt 2009) | 1 line Fix markup. ........ r75402 | georg.brandl | 2009-10-14 17:51:48 +0200 (Mi, 14 Okt 2009) | 1 line #7125: fix typo. ........ r75403 | georg.brandl | 2009-10-14 17:57:46 +0200 (Mi, 14 Okt 2009) | 1 line #7126: os.environ changes *do* take effect in subprocesses started with os.system(). ........ r75418 | georg.brandl | 2009-10-14 20:48:32 +0200 (Mi, 14 Okt 2009) | 1 line #7116: str.join() takes an iterable. ........ r75459 | georg.brandl | 2009-10-17 10:57:43 +0200 (Sa, 17 Okt 2009) | 1 line Fix refleaks in _ctypes PyCSimpleType_New, which fixes the refleak seen in test___all__. ........ r75484 | georg.brandl | 2009-10-18 09:58:12 +0200 (So, 18 Okt 2009) | 1 line Fix missing word. ........ r75592 | georg.brandl | 2009-10-22 09:05:48 +0200 (Do, 22 Okt 2009) | 1 line Fix punctuation. ........ r75593 | georg.brandl | 2009-10-22 09:06:49 +0200 (Do, 22 Okt 2009) | 1 line Revert unintended change. ........ r75594 | georg.brandl | 2009-10-22 09:56:02 +0200 (Do, 22 Okt 2009) | 1 line Fix markup. ........ r75595 | georg.brandl | 2009-10-22 09:56:56 +0200 (Do, 22 Okt 2009) | 1 line Fix duplicate target. ........ r75596 | georg.brandl | 2009-10-22 10:05:04 +0200 (Do, 22 Okt 2009) | 1 line Add a new directive marking up implementation details and start using it. ........ r75600 | georg.brandl | 2009-10-22 13:01:46 +0200 (Do, 22 Okt 2009) | 1 line Make it more robust. ........ r75602 | georg.brandl | 2009-10-22 13:28:06 +0200 (Do, 22 Okt 2009) | 1 line Document new directive. ........ r75603 | georg.brandl | 2009-10-22 13:28:23 +0200 (Do, 22 Okt 2009) | 1 line Allow short form with text as argument. ........ r75604 | georg.brandl | 2009-10-22 13:36:50 +0200 (Do, 22 Okt 2009) | 1 line Fix stylesheet for multi-paragraph impl-details. ........ r75605 | georg.brandl | 2009-10-22 13:48:10 +0200 (Do, 22 Okt 2009) | 1 line Use "impl-detail" directive where applicable. ........ r75606 | georg.brandl | 2009-10-22 17:00:06 +0200 (Do, 22 Okt 2009) | 1 line #6324: membership test tries iteration via __iter__. ........ r75607 | georg.brandl | 2009-10-22 17:04:09 +0200 (Do, 22 Okt 2009) | 1 line #7088: document new functions in signal as Unix-only. ........ r75610 | georg.brandl | 2009-10-22 17:27:24 +0200 (Do, 22 Okt 2009) | 1 line Reorder __slots__ fine print and add a clarification. ........ r75611 | georg.brandl | 2009-10-22 17:42:32 +0200 (Do, 22 Okt 2009) | 1 line #7035: improve docs of the various <method>_errors() functions, and give them docstrings. ........ r75612 | georg.brandl | 2009-10-22 17:52:15 +0200 (Do, 22 Okt 2009) | 1 line #7156: document curses as Unix-only. ........ r75613 | georg.brandl | 2009-10-22 17:54:35 +0200 (Do, 22 Okt 2009) | 1 line #6977: getopt does not support optional option arguments. ........ r75616 | georg.brandl | 2009-10-22 18:17:05 +0200 (Do, 22 Okt 2009) | 1 line Add proper references. ........ r75617 | georg.brandl | 2009-10-22 18:20:55 +0200 (Do, 22 Okt 2009) | 1 line Make printout margin important. ........ r75623 | georg.brandl | 2009-10-23 10:14:44 +0200 (Fr, 23 Okt 2009) | 1 line #7188: fix optionxform() docs. ........ r75627 | fred.drake | 2009-10-23 15:04:51 +0200 (Fr, 23 Okt 2009) | 2 lines add further note about what's passed to optionxform ........ r75640 | neil.schemenauer | 2009-10-23 21:58:17 +0200 (Fr, 23 Okt 2009) | 2 lines Improve some docstrings in the 'warnings' module. ........ r75647 | georg.brandl | 2009-10-24 12:04:19 +0200 (Sa, 24 Okt 2009) | 1 line Fix markup. ........ r75696 | georg.brandl | 2009-10-25 21:25:43 +0100 (So, 25 Okt 2009) | 1 line Fix a demo. ........ r75795 | georg.brandl | 2009-10-27 16:10:22 +0100 (Di, 27 Okt 2009) | 1 line Fix a strange mis-edit. ........
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are still reachable.
.. impl-detail::
CPython currently uses a reference-counting scheme with (optional) delayed
detection of cyclically linked garbage, which collects most objects as soon
as they become unreachable, but is not guaranteed to collect garbage
containing circular references. See the documentation of the :mod:`gc`
module for information on controlling the collection of cyclic garbage.
Other implementations act differently and CPython may change.
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Do not depend on immediate finalization of objects when they become
unreachable (so you should always close files explicitly).
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Note that the use of the implementation's tracing or debugging facilities may
keep objects alive that would normally be collectable. Also note that catching
an exception with a ':keyword:`try`...\ :keyword:`except`' statement may keep
objects alive.
Some objects contain references to "external" resources such as open files or
windows. It is understood that these resources are freed when the object is
garbage-collected, but since garbage collection is not guaranteed to happen,
such objects also provide an explicit way to release the external resource,
usually a :meth:`close` method. Programs are strongly recommended to explicitly
close such objects. The ':keyword:`try`...\ :keyword:`finally`' statement
and the ':keyword:`with`' statement provide convenient ways to do this.
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.. index:: single: container
Some objects contain references to other objects; these are called *containers*.
Examples of containers are tuples, lists and dictionaries. The references are
part of a container's value. In most cases, when we talk about the value of a
container, we imply the values, not the identities of the contained objects;
however, when we talk about the mutability of a container, only the identities
of the immediately contained objects are implied. So, if an immutable container
(like a tuple) contains a reference to a mutable object, its value changes if
that mutable object is changed.
Types affect almost all aspects of object behavior. Even the importance of
object identity is affected in some sense: for immutable types, operations that
compute new values may actually return a reference to any existing object with
the same type and value, while for mutable objects this is not allowed. E.g.,
after ``a = 1; b = 1``, ``a`` and ``b`` may or may not refer to the same object
with the value one, depending on the implementation, but after ``c = []; d =
[]``, ``c`` and ``d`` are guaranteed to refer to two different, unique, newly
created empty lists. (Note that ``c = d = []`` assigns the same object to both
``c`` and ``d``.)
.. _types:
The standard type hierarchy
===========================
.. index::
single: type
pair: data; type
pair: type; hierarchy
pair: extension; module
pair: C; language
Below is a list of the types that are built into Python. Extension modules
(written in C, Java, or other languages, depending on the implementation) can
define additional types. Future versions of Python may add types to the type
hierarchy (e.g., rational numbers, efficiently stored arrays of integers, etc.),
although such additions will often be provided via the standard library instead.
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.. index::
single: attribute
pair: special; attribute
triple: generic; special; attribute
Some of the type descriptions below contain a paragraph listing 'special
attributes.' These are attributes that provide access to the implementation and
are not intended for general use. Their definition may change in the future.
None
.. index:: object: None
This type has a single value. There is a single object with this value. This
object is accessed through the built-in name ``None``. It is used to signify the
absence of a value in many situations, e.g., it is returned from functions that
don't explicitly return anything. Its truth value is false.
NotImplemented
.. index:: object: NotImplemented
This type has a single value. There is a single object with this value. This
object is accessed through the built-in name ``NotImplemented``. Numeric methods
and rich comparison methods should return this value if they do not implement the
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operation for the operands provided. (The interpreter will then try the
reflected operation, or some other fallback, depending on the operator.) It
should not be evaluated in a boolean context.
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See
:ref:`implementing-the-arithmetic-operations`
for more details.
.. versionchanged:: 3.9
Evaluating ``NotImplemented`` in a boolean context is deprecated. While
it currently evaluates as true, it will emit a :exc:`DeprecationWarning`.
It will raise a :exc:`TypeError` in a future version of Python.
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Ellipsis
.. index::
object: Ellipsis
single: ...; ellipsis literal
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This type has a single value. There is a single object with this value. This
object is accessed through the literal ``...`` or the built-in name
``Ellipsis``. Its truth value is true.
Merged revisions 59666-59679 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59666 | christian.heimes | 2008-01-02 19:28:32 +0100 (Wed, 02 Jan 2008) | 1 line Made vs9to8 Unix compatible ........ r59669 | guido.van.rossum | 2008-01-02 20:00:46 +0100 (Wed, 02 Jan 2008) | 2 lines Patch #1696. Don't attempt to close None in dry-run mode. ........ r59671 | jeffrey.yasskin | 2008-01-03 03:21:52 +0100 (Thu, 03 Jan 2008) | 6 lines Backport PEP 3141 from the py3k branch to the trunk. This includes r50877 (just the complex_pow part), r56649, r56652, r56715, r57296, r57302, r57359, r57361, r57372, r57738, r57739, r58017, r58039, r58040, and r59390, and new documentation. The only significant difference is that round(x) returns a float to preserve backward-compatibility. See http://bugs.python.org/issue1689. ........ r59672 | christian.heimes | 2008-01-03 16:41:30 +0100 (Thu, 03 Jan 2008) | 1 line Issue #1726: Remove Python/atof.c from PCBuild/pythoncore.vcproj ........ r59675 | guido.van.rossum | 2008-01-03 20:12:44 +0100 (Thu, 03 Jan 2008) | 4 lines Issue #1700, reported by Nguyen Quan Son, fix by Fredruk Lundh: Regular Expression inline flags not handled correctly for some unicode characters. (Forward port from 2.5.2.) ........ r59676 | christian.heimes | 2008-01-03 21:23:15 +0100 (Thu, 03 Jan 2008) | 1 line Added math.isinf() and math.isnan() ........ r59677 | christian.heimes | 2008-01-03 22:14:48 +0100 (Thu, 03 Jan 2008) | 1 line Some build bots don't compile mathmodule. There is an issue with the long definition of pi and euler ........ r59678 | christian.heimes | 2008-01-03 23:16:32 +0100 (Thu, 03 Jan 2008) | 2 lines Modified PyImport_Import and PyImport_ImportModule to always use absolute imports by calling __import__ with an explicit level of 0 Added a new API function PyImport_ImportModuleNoBlock. It solves the problem with dead locks when mixing threads and imports ........ r59679 | christian.heimes | 2008-01-03 23:32:26 +0100 (Thu, 03 Jan 2008) | 1 line Added copysign(x, y) function to the math module ........
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:class:`numbers.Number`
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.. index:: object: numeric
These are created by numeric literals and returned as results by arithmetic
operators and arithmetic built-in functions. Numeric objects are immutable;
once created their value never changes. Python numbers are of course strongly
related to mathematical numbers, but subject to the limitations of numerical
representation in computers.
The string representations of the numeric classes, computed by
:meth:`__repr__` and :meth:`__str__`, have the following
properties:
* They are valid numeric literals which, when passed to their
class constructor, produce an object having the value of the
original numeric.
* The representation is in base 10, when possible.
* Leading zeros, possibly excepting a single zero before a
decimal point, are not shown.
* Trailing zeros, possibly excepting a single zero after a
decimal point, are not shown.
* A sign is shown only when the number is negative.
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Python distinguishes between integers, floating point numbers, and complex
numbers:
Merged revisions 59666-59679 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59666 | christian.heimes | 2008-01-02 19:28:32 +0100 (Wed, 02 Jan 2008) | 1 line Made vs9to8 Unix compatible ........ r59669 | guido.van.rossum | 2008-01-02 20:00:46 +0100 (Wed, 02 Jan 2008) | 2 lines Patch #1696. Don't attempt to close None in dry-run mode. ........ r59671 | jeffrey.yasskin | 2008-01-03 03:21:52 +0100 (Thu, 03 Jan 2008) | 6 lines Backport PEP 3141 from the py3k branch to the trunk. This includes r50877 (just the complex_pow part), r56649, r56652, r56715, r57296, r57302, r57359, r57361, r57372, r57738, r57739, r58017, r58039, r58040, and r59390, and new documentation. The only significant difference is that round(x) returns a float to preserve backward-compatibility. See http://bugs.python.org/issue1689. ........ r59672 | christian.heimes | 2008-01-03 16:41:30 +0100 (Thu, 03 Jan 2008) | 1 line Issue #1726: Remove Python/atof.c from PCBuild/pythoncore.vcproj ........ r59675 | guido.van.rossum | 2008-01-03 20:12:44 +0100 (Thu, 03 Jan 2008) | 4 lines Issue #1700, reported by Nguyen Quan Son, fix by Fredruk Lundh: Regular Expression inline flags not handled correctly for some unicode characters. (Forward port from 2.5.2.) ........ r59676 | christian.heimes | 2008-01-03 21:23:15 +0100 (Thu, 03 Jan 2008) | 1 line Added math.isinf() and math.isnan() ........ r59677 | christian.heimes | 2008-01-03 22:14:48 +0100 (Thu, 03 Jan 2008) | 1 line Some build bots don't compile mathmodule. There is an issue with the long definition of pi and euler ........ r59678 | christian.heimes | 2008-01-03 23:16:32 +0100 (Thu, 03 Jan 2008) | 2 lines Modified PyImport_Import and PyImport_ImportModule to always use absolute imports by calling __import__ with an explicit level of 0 Added a new API function PyImport_ImportModuleNoBlock. It solves the problem with dead locks when mixing threads and imports ........ r59679 | christian.heimes | 2008-01-03 23:32:26 +0100 (Thu, 03 Jan 2008) | 1 line Added copysign(x, y) function to the math module ........
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:class:`numbers.Integral`
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.. index:: object: integer
These represent elements from the mathematical set of integers (positive and
negative).
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There are two types of integers:
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Integers (:class:`int`)
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These represent numbers in an unlimited range, subject to available (virtual)
memory only. For the purpose of shift and mask operations, a binary
representation is assumed, and negative numbers are represented in a variant of
2's complement which gives the illusion of an infinite string of sign bits
extending to the left.
Booleans (:class:`bool`)
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.. index::
object: Boolean
single: False
single: True
These represent the truth values False and True. The two objects representing
the values ``False`` and ``True`` are the only Boolean objects. The Boolean type is a
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subtype of the integer type, and Boolean values behave like the values 0 and 1,
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respectively, in almost all contexts, the exception being that when converted to
a string, the strings ``"False"`` or ``"True"`` are returned, respectively.
.. index:: pair: integer; representation
The rules for integer representation are intended to give the most meaningful
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interpretation of shift and mask operations involving negative integers.
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Merged revisions 59666-59679 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59666 | christian.heimes | 2008-01-02 19:28:32 +0100 (Wed, 02 Jan 2008) | 1 line Made vs9to8 Unix compatible ........ r59669 | guido.van.rossum | 2008-01-02 20:00:46 +0100 (Wed, 02 Jan 2008) | 2 lines Patch #1696. Don't attempt to close None in dry-run mode. ........ r59671 | jeffrey.yasskin | 2008-01-03 03:21:52 +0100 (Thu, 03 Jan 2008) | 6 lines Backport PEP 3141 from the py3k branch to the trunk. This includes r50877 (just the complex_pow part), r56649, r56652, r56715, r57296, r57302, r57359, r57361, r57372, r57738, r57739, r58017, r58039, r58040, and r59390, and new documentation. The only significant difference is that round(x) returns a float to preserve backward-compatibility. See http://bugs.python.org/issue1689. ........ r59672 | christian.heimes | 2008-01-03 16:41:30 +0100 (Thu, 03 Jan 2008) | 1 line Issue #1726: Remove Python/atof.c from PCBuild/pythoncore.vcproj ........ r59675 | guido.van.rossum | 2008-01-03 20:12:44 +0100 (Thu, 03 Jan 2008) | 4 lines Issue #1700, reported by Nguyen Quan Son, fix by Fredruk Lundh: Regular Expression inline flags not handled correctly for some unicode characters. (Forward port from 2.5.2.) ........ r59676 | christian.heimes | 2008-01-03 21:23:15 +0100 (Thu, 03 Jan 2008) | 1 line Added math.isinf() and math.isnan() ........ r59677 | christian.heimes | 2008-01-03 22:14:48 +0100 (Thu, 03 Jan 2008) | 1 line Some build bots don't compile mathmodule. There is an issue with the long definition of pi and euler ........ r59678 | christian.heimes | 2008-01-03 23:16:32 +0100 (Thu, 03 Jan 2008) | 2 lines Modified PyImport_Import and PyImport_ImportModule to always use absolute imports by calling __import__ with an explicit level of 0 Added a new API function PyImport_ImportModuleNoBlock. It solves the problem with dead locks when mixing threads and imports ........ r59679 | christian.heimes | 2008-01-03 23:32:26 +0100 (Thu, 03 Jan 2008) | 1 line Added copysign(x, y) function to the math module ........
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:class:`numbers.Real` (:class:`float`)
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.. index::
object: floating point
pair: floating point; number
pair: C; language
pair: Java; language
These represent machine-level double precision floating point numbers. You are
at the mercy of the underlying machine architecture (and C or Java
implementation) for the accepted range and handling of overflow. Python does not
support single-precision floating point numbers; the savings in processor and
memory usage that are usually the reason for using these are dwarfed by the
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overhead of using objects in Python, so there is no reason to complicate the
language with two kinds of floating point numbers.
:class:`numbers.Complex` (:class:`complex`)
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.. index::
object: complex
pair: complex; number
These represent complex numbers as a pair of machine-level double precision
floating point numbers. The same caveats apply as for floating point numbers.
The real and imaginary parts of a complex number ``z`` can be retrieved through
the read-only attributes ``z.real`` and ``z.imag``.
Sequences
.. index::
builtin: len
object: sequence
single: index operation
single: item selection
single: subscription
These represent finite ordered sets indexed by non-negative numbers. The
built-in function :func:`len` returns the number of items of a sequence. When
the length of a sequence is *n*, the index set contains the numbers 0, 1,
..., *n*-1. Item *i* of sequence *a* is selected by ``a[i]``.
.. index:: single: slicing
Sequences also support slicing: ``a[i:j]`` selects all items with index *k* such
that *i* ``<=`` *k* ``<`` *j*. When used as an expression, a slice is a
sequence of the same type. This implies that the index set is renumbered so
that it starts at 0.
Some sequences also support "extended slicing" with a third "step" parameter:
``a[i:j:k]`` selects all items of *a* with index *x* where ``x = i + n*k``, *n*
``>=`` ``0`` and *i* ``<=`` *x* ``<`` *j*.
Sequences are distinguished according to their mutability:
Immutable sequences
.. index::
object: immutable sequence
object: immutable
An object of an immutable sequence type cannot change once it is created. (If
the object contains references to other objects, these other objects may be
mutable and may be changed; however, the collection of objects directly
referenced by an immutable object cannot change.)
The following types are immutable sequences:
.. index::
single: string; immutable sequences
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Strings
.. index::
builtin: chr
builtin: ord
single: character
single: integer
single: Unicode
A string is a sequence of values that represent Unicode code points.
All the code points in the range ``U+0000 - U+10FFFF`` can be
represented in a string. Python doesn't have a :c:type:`char` type;
instead, every code point in the string is represented as a string
object with length ``1``. The built-in function :func:`ord`
converts a code point from its string form to an integer in the
range ``0 - 10FFFF``; :func:`chr` converts an integer in the range
``0 - 10FFFF`` to the corresponding length ``1`` string object.
:meth:`str.encode` can be used to convert a :class:`str` to
:class:`bytes` using the given text encoding, and
:meth:`bytes.decode` can be used to achieve the opposite.
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Tuples
.. index::
object: tuple
pair: singleton; tuple
pair: empty; tuple
The items of a tuple are arbitrary Python objects. Tuples of two or
more items are formed by comma-separated lists of expressions. A tuple
of one item (a 'singleton') can be formed by affixing a comma to an
expression (an expression by itself does not create a tuple, since
parentheses must be usable for grouping of expressions). An empty
tuple can be formed by an empty pair of parentheses.
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Bytes
.. index:: bytes, byte
A bytes object is an immutable array. The items are 8-bit bytes,
represented by integers in the range 0 <= x < 256. Bytes literals
(like ``b'abc'``) and the built-in :func:`bytes()` constructor
can be used to create bytes objects. Also, bytes objects can be
decoded to strings via the :meth:`~bytes.decode` method.
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Mutable sequences
.. index::
object: mutable sequence
object: mutable
pair: assignment; statement
single: subscription
single: slicing
Mutable sequences can be changed after they are created. The subscription and
slicing notations can be used as the target of assignment and :keyword:`del`
(delete) statements.
Merged revisions 68633,68648,68667,68706,68718,68720-68721,68724-68727,68739 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r68633 | thomas.heller | 2009-01-16 12:53:44 -0600 (Fri, 16 Jan 2009) | 3 lines Change an example in the docs to avoid a mistake when the code is copy pasted and changed afterwards. ........ r68648 | benjamin.peterson | 2009-01-16 22:28:57 -0600 (Fri, 16 Jan 2009) | 1 line use enumerate ........ r68667 | amaury.forgeotdarc | 2009-01-17 14:18:59 -0600 (Sat, 17 Jan 2009) | 3 lines #4077: No need to append \n when calling Py_FatalError + fix a declaration to make it match the one in pythonrun.h ........ r68706 | benjamin.peterson | 2009-01-17 19:28:46 -0600 (Sat, 17 Jan 2009) | 1 line fix grammar ........ r68718 | georg.brandl | 2009-01-18 04:42:35 -0600 (Sun, 18 Jan 2009) | 1 line #4976: union() and intersection() take multiple args, but talk about "the other". ........ r68720 | georg.brandl | 2009-01-18 04:45:22 -0600 (Sun, 18 Jan 2009) | 1 line #4974: fix redundant mention of lists and tuples. ........ r68721 | georg.brandl | 2009-01-18 04:48:16 -0600 (Sun, 18 Jan 2009) | 1 line #4914: trunc is in math. ........ r68724 | georg.brandl | 2009-01-18 07:24:10 -0600 (Sun, 18 Jan 2009) | 1 line #4979: correct result range for some random functions. ........ r68725 | georg.brandl | 2009-01-18 07:47:26 -0600 (Sun, 18 Jan 2009) | 1 line #4857: fix augmented assignment target spec. ........ r68726 | georg.brandl | 2009-01-18 08:41:52 -0600 (Sun, 18 Jan 2009) | 1 line #4923: clarify what was added. ........ r68727 | georg.brandl | 2009-01-18 12:25:30 -0600 (Sun, 18 Jan 2009) | 1 line #4986: augassigns are not expressions. ........ r68739 | benjamin.peterson | 2009-01-18 15:11:38 -0600 (Sun, 18 Jan 2009) | 1 line fix test that wasn't working as expected #4990 ........
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There are currently two intrinsic mutable sequence types:
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Lists
.. index:: object: list
The items of a list are arbitrary Python objects. Lists are formed by
placing a comma-separated list of expressions in square brackets. (Note
that there are no special cases needed to form lists of length 0 or 1.)
Byte Arrays
.. index:: bytearray
A bytearray object is a mutable array. They are created by the built-in
:func:`bytearray` constructor. Aside from being mutable
(and hence unhashable), byte arrays otherwise provide the same interface
and functionality as immutable :class:`bytes` objects.
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.. index:: module: array
The extension module :mod:`array` provides an additional example of a
mutable sequence type, as does the :mod:`collections` module.
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Set types
.. index::
builtin: len
object: set type
These represent unordered, finite sets of unique, immutable objects. As such,
they cannot be indexed by any subscript. However, they can be iterated over, and
the built-in function :func:`len` returns the number of items in a set. Common
uses for sets are fast membership testing, removing duplicates from a sequence,
and computing mathematical operations such as intersection, union, difference,
and symmetric difference.
For set elements, the same immutability rules apply as for dictionary keys. Note
that numeric types obey the normal rules for numeric comparison: if two numbers
compare equal (e.g., ``1`` and ``1.0``), only one of them can be contained in a
set.
There are currently two intrinsic set types:
Sets
.. index:: object: set
These represent a mutable set. They are created by the built-in :func:`set`
constructor and can be modified afterwards by several methods, such as
:meth:`~set.add`.
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Frozen sets
.. index:: object: frozenset
Merged revisions 58742-58816 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r58745 | georg.brandl | 2007-11-01 10:19:33 -0700 (Thu, 01 Nov 2007) | 2 lines #1364: os.lstat is available on Windows too, as an alias to os.stat. ........ r58750 | christian.heimes | 2007-11-01 12:48:10 -0700 (Thu, 01 Nov 2007) | 1 line Backport of import tests for bug http://bugs.python.org/issue1293 and bug http://bugs.python.org/issue1342 ........ r58751 | christian.heimes | 2007-11-01 13:11:06 -0700 (Thu, 01 Nov 2007) | 1 line Removed non ASCII text from test as requested by Guido. Sorry :/ ........ r58753 | georg.brandl | 2007-11-01 13:37:02 -0700 (Thu, 01 Nov 2007) | 2 lines Fix markup glitch. ........ r58757 | gregory.p.smith | 2007-11-01 14:08:14 -0700 (Thu, 01 Nov 2007) | 4 lines Fix bug introduced in revision 58385. Database keys could no longer have NULL bytes in them. Replace the errant strdup with a malloc+memcpy. Adds a unit test for the correct behavior. ........ r58758 | gregory.p.smith | 2007-11-01 14:15:36 -0700 (Thu, 01 Nov 2007) | 3 lines Undo revision 58533 58534 fixes. Those were a workaround for a problem introduced by 58385. ........ r58759 | gregory.p.smith | 2007-11-01 14:17:47 -0700 (Thu, 01 Nov 2007) | 2 lines false "fix" undone as correct problem was found and fixed. ........ r58765 | mark.summerfield | 2007-11-02 01:24:59 -0700 (Fri, 02 Nov 2007) | 3 lines Added more file-handling related cross-references. ........ r58766 | nick.coghlan | 2007-11-02 03:09:12 -0700 (Fri, 02 Nov 2007) | 1 line Fix for bug 1705170 - contextmanager swallowing StopIteration (2.5 backport candidate) ........ r58784 | thomas.heller | 2007-11-02 12:10:24 -0700 (Fri, 02 Nov 2007) | 4 lines Issue #1292: On alpha, arm, ppc, and s390 linux systems the --with-system-ffi configure option defaults to "yes" because the bundled libffi sources are too old. ........ r58785 | thomas.heller | 2007-11-02 12:11:23 -0700 (Fri, 02 Nov 2007) | 1 line Enable the full ctypes c_longdouble tests again. ........ r58796 | georg.brandl | 2007-11-02 13:06:17 -0700 (Fri, 02 Nov 2007) | 4 lines Make "hashable" a glossary entry and clarify docs on __cmp__, __eq__ and __hash__. I hope the concept of hashability is better understandable now. Thanks to Tim Hatch for pointing out the flaws here. ........
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These represent an immutable set. They are created by the built-in
:func:`frozenset` constructor. As a frozenset is immutable and
:term:`hashable`, it can be used again as an element of another set, or as
a dictionary key.
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Mappings
.. index::
builtin: len
single: subscription
object: mapping
These represent finite sets of objects indexed by arbitrary index sets. The
subscript notation ``a[k]`` selects the item indexed by ``k`` from the mapping
``a``; this can be used in expressions and as the target of assignments or
:keyword:`del` statements. The built-in function :func:`len` returns the number
of items in a mapping.
There is currently a single intrinsic mapping type:
Dictionaries
.. index:: object: dictionary
These represent finite sets of objects indexed by nearly arbitrary values. The
only types of values not acceptable as keys are values containing lists or
dictionaries or other mutable types that are compared by value rather than by
object identity, the reason being that the efficient implementation of
dictionaries requires a key's hash value to remain constant. Numeric types used
for keys obey the normal rules for numeric comparison: if two numbers compare
equal (e.g., ``1`` and ``1.0``) then they can be used interchangeably to index
the same dictionary entry.
Dictionaries preserve insertion order, meaning that keys will be produced
in the same order they were added sequentially over the dictionary.
Replacing an existing key does not change the order, however removing a key
and re-inserting it will add it to the end instead of keeping its old place.
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Dictionaries are mutable; they can be created by the ``{...}`` notation (see
section :ref:`dict`).
.. index::
module: dbm.ndbm
module: dbm.gnu
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The extension modules :mod:`dbm.ndbm` and :mod:`dbm.gnu` provide
additional examples of mapping types, as does the :mod:`collections`
module.
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.. versionchanged:: 3.7
Dictionaries did not preserve insertion order in versions of Python before 3.6.
In CPython 3.6, insertion order was preserved, but it was considered
an implementation detail at that time rather than a language guarantee.
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Callable types
.. index::
object: callable
pair: function; call
single: invocation
pair: function; argument
These are the types to which the function call operation (see section
:ref:`calls`) can be applied:
User-defined functions
.. index::
pair: user-defined; function
object: function
object: user-defined function
A user-defined function object is created by a function definition (see
section :ref:`function`). It should be called with an argument list
containing the same number of items as the function's formal parameter
list.
Special attributes:
.. tabularcolumns:: |l|L|l|
.. index::
single: __doc__ (function attribute)
single: __name__ (function attribute)
single: __module__ (function attribute)
single: __dict__ (function attribute)
single: __defaults__ (function attribute)
single: __closure__ (function attribute)
single: __code__ (function attribute)
single: __globals__ (function attribute)
single: __annotations__ (function attribute)
single: __kwdefaults__ (function attribute)
pair: global; namespace
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+-------------------------+-------------------------------+-----------+
| Attribute | Meaning | |
+=========================+===============================+===========+
| :attr:`__doc__` | The function's documentation | Writable |
| | string, or ``None`` if | |
| | unavailable; not inherited by | |
| | subclasses. | |
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+-------------------------+-------------------------------+-----------+
| :attr:`~definition.\ | The function's name. | Writable |
| __name__` | | |
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+-------------------------+-------------------------------+-----------+
| :attr:`~definition.\ | The function's | Writable |
| __qualname__` | :term:`qualified name`. | |
| | | |
| | .. versionadded:: 3.3 | |
+-------------------------+-------------------------------+-----------+
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| :attr:`__module__` | The name of the module the | Writable |
| | function was defined in, or | |
| | ``None`` if unavailable. | |
+-------------------------+-------------------------------+-----------+
| :attr:`__defaults__` | A tuple containing default | Writable |
| | argument values for those | |
| | arguments that have defaults, | |
| | or ``None`` if no arguments | |
| | have a default value. | |
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+-------------------------+-------------------------------+-----------+
| :attr:`__code__` | The code object representing | Writable |
| | the compiled function body. | |
+-------------------------+-------------------------------+-----------+
| :attr:`__globals__` | A reference to the dictionary | Read-only |
| | that holds the function's | |
| | global variables --- the | |
| | global namespace of the | |
| | module in which the function | |
| | was defined. | |
+-------------------------+-------------------------------+-----------+
| :attr:`~object.__dict__`| The namespace supporting | Writable |
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| | arbitrary function | |
| | attributes. | |
+-------------------------+-------------------------------+-----------+
| :attr:`__closure__` | ``None`` or a tuple of cells | Read-only |
| | that contain bindings for the | |
| | function's free variables. | |
| | See below for information on | |
| | the ``cell_contents`` | |
| | attribute. | |
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+-------------------------+-------------------------------+-----------+
| :attr:`__annotations__` | A dict containing annotations | Writable |
| | of parameters. The keys of | |
| | the dict are the parameter | |
| | names, and ``'return'`` for | |
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| | the return annotation, if | |
| | provided. For more | |
| | information on working with | |
| | this attribute, see | |
| | :ref:`annotations-howto`. | |
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+-------------------------+-------------------------------+-----------+
| :attr:`__kwdefaults__` | A dict containing defaults | Writable |
| | for keyword-only parameters. | |
+-------------------------+-------------------------------+-----------+
Most of the attributes labelled "Writable" check the type of the assigned value.
Function objects also support getting and setting arbitrary attributes, which
can be used, for example, to attach metadata to functions. Regular attribute
dot-notation is used to get and set such attributes. *Note that the current
implementation only supports function attributes on user-defined functions.
Function attributes on built-in functions may be supported in the future.*
A cell object has the attribute ``cell_contents``. This can be used to get
the value of the cell, as well as set the value.
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Additional information about a function's definition can be retrieved from its
code object; see the description of internal types below. The
:data:`cell <types.CellType>` type can be accessed in the :mod:`types`
module.
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Instance methods
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.. index::
object: method
object: user-defined method
pair: user-defined; method
An instance method object combines a class, a class instance and any
callable object (normally a user-defined function).
.. index::
single: __func__ (method attribute)
single: __self__ (method attribute)
single: __doc__ (method attribute)
single: __name__ (method attribute)
single: __module__ (method attribute)
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Special read-only attributes: :attr:`__self__` is the class instance object,
:attr:`__func__` is the function object; :attr:`__doc__` is the method's
documentation (same as ``__func__.__doc__``); :attr:`~definition.__name__` is the
method name (same as ``__func__.__name__``); :attr:`__module__` is the
name of the module the method was defined in, or ``None`` if unavailable.
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Methods also support accessing (but not setting) the arbitrary function
attributes on the underlying function object.
User-defined method objects may be created when getting an attribute of a
class (perhaps via an instance of that class), if that attribute is a
user-defined function object or a class method object.
When an instance method object is created by retrieving a user-defined
function object from a class via one of its instances, its
:attr:`__self__` attribute is the instance, and the method object is said
to be bound. The new method's :attr:`__func__` attribute is the original
function object.
When an instance method object is created by retrieving a class method
object from a class or instance, its :attr:`__self__` attribute is the
class itself, and its :attr:`__func__` attribute is the function object
underlying the class method.
When an instance method object is called, the underlying function
(:attr:`__func__`) is called, inserting the class instance
(:attr:`__self__`) in front of the argument list. For instance, when
:class:`C` is a class which contains a definition for a function
:meth:`f`, and ``x`` is an instance of :class:`C`, calling ``x.f(1)`` is
equivalent to calling ``C.f(x, 1)``.
When an instance method object is derived from a class method object, the
"class instance" stored in :attr:`__self__` will actually be the class
itself, so that calling either ``x.f(1)`` or ``C.f(1)`` is equivalent to
calling ``f(C,1)`` where ``f`` is the underlying function.
Note that the transformation from function object to instance method
object happens each time the attribute is retrieved from the instance. In
some cases, a fruitful optimization is to assign the attribute to a local
variable and call that local variable. Also notice that this
transformation only happens for user-defined functions; other callable
objects (and all non-callable objects) are retrieved without
transformation. It is also important to note that user-defined functions
which are attributes of a class instance are not converted to bound
methods; this *only* happens when the function is an attribute of the
class.
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Generator functions
.. index::
single: generator; function
single: generator; iterator
A function or method which uses the :keyword:`yield` statement (see section
:ref:`yield`) is called a :dfn:`generator function`. Such a function, when
called, always returns an iterator object which can be used to execute the
body of the function: calling the iterator's :meth:`iterator.__next__`
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method will cause the function to execute until it provides a value
using the :keyword:`!yield` statement. When the function executes a
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:keyword:`return` statement or falls off the end, a :exc:`StopIteration`
exception is raised and the iterator will have reached the end of the set of
values to be returned.
Coroutine functions
.. index::
single: coroutine; function
A function or method which is defined using :keyword:`async def` is called
a :dfn:`coroutine function`. Such a function, when called, returns a
:term:`coroutine` object. It may contain :keyword:`await` expressions,
as well as :keyword:`async with` and :keyword:`async for` statements. See
also the :ref:`coroutine-objects` section.
Asynchronous generator functions
.. index::
single: asynchronous generator; function
single: asynchronous generator; asynchronous iterator
A function or method which is defined using :keyword:`async def` and
which uses the :keyword:`yield` statement is called a
:dfn:`asynchronous generator function`. Such a function, when called,
returns an asynchronous iterator object which can be used in an
:keyword:`async for` statement to execute the body of the function.
Calling the asynchronous iterator's :meth:`aiterator.__anext__` method
will return an :term:`awaitable` which when awaited
will execute until it provides a value using the :keyword:`yield`
expression. When the function executes an empty :keyword:`return`
statement or falls off the end, a :exc:`StopAsyncIteration` exception
is raised and the asynchronous iterator will have reached the end of
the set of values to be yielded.
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Built-in functions
.. index::
object: built-in function
object: function
pair: C; language
A built-in function object is a wrapper around a C function. Examples of
built-in functions are :func:`len` and :func:`math.sin` (:mod:`math` is a
standard built-in module). The number and type of the arguments are
determined by the C function. Special read-only attributes:
:attr:`__doc__` is the function's documentation string, or ``None`` if
unavailable; :attr:`~definition.__name__` is the function's name; :attr:`__self__` is
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set to ``None`` (but see the next item); :attr:`__module__` is the name of
the module the function was defined in or ``None`` if unavailable.
Built-in methods
.. index::
object: built-in method
object: method
pair: built-in; method
This is really a different disguise of a built-in function, this time containing
an object passed to the C function as an implicit extra argument. An example of
a built-in method is ``alist.append()``, assuming *alist* is a list object. In
this case, the special read-only attribute :attr:`__self__` is set to the object
denoted by *alist*.
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Classes
Classes are callable. These objects normally act as factories for new
instances of themselves, but variations are possible for class types that
override :meth:`__new__`. The arguments of the call are passed to
:meth:`__new__` and, in the typical case, to :meth:`__init__` to
initialize the new instance.
Class Instances
Instances of arbitrary classes can be made callable by defining a
:meth:`__call__` method in their class.
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Modules
.. index::
statement: import
object: module
Modules are a basic organizational unit of Python code, and are created by
the :ref:`import system <importsystem>` as invoked either by the
:keyword:`import` statement, or by calling
functions such as :func:`importlib.import_module` and built-in
:func:`__import__`. A module object has a namespace implemented by a
dictionary object (this is the dictionary referenced by the ``__globals__``
attribute of functions defined in the module). Attribute references are
translated to lookups in this dictionary, e.g., ``m.x`` is equivalent to
``m.__dict__["x"]``. A module object does not contain the code object used
to initialize the module (since it isn't needed once the initialization is
done).
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Attribute assignment updates the module's namespace dictionary, e.g.,
``m.x = 1`` is equivalent to ``m.__dict__["x"] = 1``.
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.. index::
single: __name__ (module attribute)
single: __doc__ (module attribute)
single: __file__ (module attribute)
single: __annotations__ (module attribute)
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pair: module; namespace
Predefined (writable) attributes:
:attr:`__name__`
The module's name.
:attr:`__doc__`
The module's documentation string, or ``None`` if
unavailable.
:attr:`__file__`
The pathname of the file from which the
module was loaded, if it was loaded from a file.
The :attr:`__file__`
attribute may be missing for certain types of modules, such as C modules
that are statically linked into the interpreter. For extension modules
loaded dynamically from a shared library, it's the pathname of the shared
library file.
:attr:`__annotations__`
A dictionary containing
:term:`variable annotations <variable annotation>` collected during
module body execution. For best practices on working
with :attr:`__annotations__`, please see :ref:`annotations-howto`.
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.. index:: single: __dict__ (module attribute)
Special read-only attribute: :attr:`~object.__dict__` is the module's
namespace as a dictionary object.
.. impl-detail::
Because of the way CPython clears module dictionaries, the module
dictionary will be cleared when the module falls out of scope even if the
dictionary still has live references. To avoid this, copy the dictionary
or keep the module around while using its dictionary directly.
Custom classes
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Custom class types are typically created by class definitions (see section
:ref:`class`). A class has a namespace implemented by a dictionary object.
Class attribute references are translated to lookups in this dictionary, e.g.,
``C.x`` is translated to ``C.__dict__["x"]`` (although there are a number of
hooks which allow for other means of locating attributes). When the attribute
name is not found there, the attribute search continues in the base classes.
This search of the base classes uses the C3 method resolution order which
behaves correctly even in the presence of 'diamond' inheritance structures
where there are multiple inheritance paths leading back to a common ancestor.
Additional details on the C3 MRO used by Python can be found in the
documentation accompanying the 2.3 release at
https://www.python.org/download/releases/2.3/mro/.
.. XXX: Could we add that MRO doc as an appendix to the language ref?
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.. index::
object: class
object: class instance
object: instance
pair: class object; call
single: container
object: dictionary
pair: class; attribute
When a class attribute reference (for class :class:`C`, say) would yield a
class method object, it is transformed into an instance method object whose
:attr:`__self__` attribute is :class:`C`. When it would yield a static
method object, it is transformed into the object wrapped by the static method
object. See section :ref:`descriptors` for another way in which attributes
retrieved from a class may differ from those actually contained in its
:attr:`~object.__dict__`.
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.. index:: triple: class; attribute; assignment
Class attribute assignments update the class's dictionary, never the dictionary
of a base class.
.. index:: pair: class object; call
A class object can be called (see above) to yield a class instance (see below).
.. index::
single: __name__ (class attribute)
single: __module__ (class attribute)
single: __dict__ (class attribute)
single: __bases__ (class attribute)
single: __doc__ (class attribute)
single: __annotations__ (class attribute)
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Special attributes:
:attr:`~definition.__name__`
The class name.
:attr:`__module__`
The name of the module in which the class was defined.
:attr:`~object.__dict__`
The dictionary containing the class's namespace.
:attr:`~class.__bases__`
A tuple containing the base classes, in the order of
their occurrence in the base class list.
:attr:`__doc__`
The class's documentation string, or ``None`` if undefined.
:attr:`__annotations__`
A dictionary containing
:term:`variable annotations <variable annotation>`
collected during class body execution. For best practices on
working with :attr:`__annotations__`, please see
:ref:`annotations-howto`.
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Class instances
.. index::
object: class instance
object: instance
pair: class; instance
pair: class instance; attribute
A class instance is created by calling a class object (see above). A class
instance has a namespace implemented as a dictionary which is the first place
in which attribute references are searched. When an attribute is not found
there, and the instance's class has an attribute by that name, the search
continues with the class attributes. If a class attribute is found that is a
user-defined function object, it is transformed into an instance method
object whose :attr:`__self__` attribute is the instance. Static method and
class method objects are also transformed; see above under "Classes". See
section :ref:`descriptors` for another way in which attributes of a class
retrieved via its instances may differ from the objects actually stored in
the class's :attr:`~object.__dict__`. If no class attribute is found, and the
object's class has a :meth:`__getattr__` method, that is called to satisfy
the lookup.
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.. index:: triple: class instance; attribute; assignment
Attribute assignments and deletions update the instance's dictionary, never a
class's dictionary. If the class has a :meth:`__setattr__` or
:meth:`__delattr__` method, this is called instead of updating the instance
dictionary directly.
.. index::
object: numeric
object: sequence
object: mapping
Class instances can pretend to be numbers, sequences, or mappings if they have
methods with certain special names. See section :ref:`specialnames`.
.. index::
single: __dict__ (instance attribute)
single: __class__ (instance attribute)
Special attributes: :attr:`~object.__dict__` is the attribute dictionary;
:attr:`~instance.__class__` is the instance's class.
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I/O objects (also known as file objects)
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.. index::
builtin: open
module: io
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single: popen() (in module os)
single: makefile() (socket method)
single: sys.stdin
single: sys.stdout
single: sys.stderr
single: stdio
single: stdin (in module sys)
single: stdout (in module sys)
single: stderr (in module sys)
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A :term:`file object` represents an open file. Various shortcuts are
available to create file objects: the :func:`open` built-in function, and
also :func:`os.popen`, :func:`os.fdopen`, and the
:meth:`~socket.socket.makefile` method of socket objects (and perhaps by
other functions or methods provided by extension modules).
The objects ``sys.stdin``, ``sys.stdout`` and ``sys.stderr`` are
initialized to file objects corresponding to the interpreter's standard
input, output and error streams; they are all open in text mode and
therefore follow the interface defined by the :class:`io.TextIOBase`
abstract class.
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Internal types
.. index::
single: internal type
single: types, internal
A few types used internally by the interpreter are exposed to the user. Their
definitions may change with future versions of the interpreter, but they are
mentioned here for completeness.
.. index:: bytecode, object; code, code object
2007-08-15 11:28:22 -03:00
Code objects
#1370: Finish the merge r58749, log below, by resolving all conflicts in Doc/. Merged revisions 58221-58741 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r58221 | georg.brandl | 2007-09-20 10:57:59 -0700 (Thu, 20 Sep 2007) | 2 lines Patch #1181: add os.environ.clear() method. ........ r58225 | sean.reifschneider | 2007-09-20 23:33:28 -0700 (Thu, 20 Sep 2007) | 3 lines Issue1704287: "make install" fails unless you do "make" first. Make oldsharedmods and sharedmods in "libinstall". ........ r58232 | guido.van.rossum | 2007-09-22 13:18:03 -0700 (Sat, 22 Sep 2007) | 4 lines Patch # 188 by Philip Jenvey. Make tell() mark CRLF as a newline. With unit test. ........ r58242 | georg.brandl | 2007-09-24 10:55:47 -0700 (Mon, 24 Sep 2007) | 2 lines Fix typo and double word. ........ r58245 | georg.brandl | 2007-09-24 10:59:28 -0700 (Mon, 24 Sep 2007) | 2 lines #1196: document default radix for int(). ........ r58247 | georg.brandl | 2007-09-24 11:08:24 -0700 (Mon, 24 Sep 2007) | 2 lines #1177: accept 2xx responses for https too, not only http. ........ r58249 | andrew.kuchling | 2007-09-24 16:45:51 -0700 (Mon, 24 Sep 2007) | 1 line Remove stray odd character; grammar fix ........ r58250 | andrew.kuchling | 2007-09-24 16:46:28 -0700 (Mon, 24 Sep 2007) | 1 line Typo fix ........ r58251 | andrew.kuchling | 2007-09-24 17:09:42 -0700 (Mon, 24 Sep 2007) | 1 line Add various items ........ r58268 | vinay.sajip | 2007-09-26 22:34:45 -0700 (Wed, 26 Sep 2007) | 1 line Change to flush and close logic to fix #1760556. ........ r58269 | vinay.sajip | 2007-09-26 22:38:51 -0700 (Wed, 26 Sep 2007) | 1 line Change to basicConfig() to fix #1021. ........ r58270 | georg.brandl | 2007-09-26 23:26:58 -0700 (Wed, 26 Sep 2007) | 2 lines #1208: document match object's boolean value. ........ r58271 | vinay.sajip | 2007-09-26 23:56:13 -0700 (Wed, 26 Sep 2007) | 1 line Minor date change. ........ r58272 | vinay.sajip | 2007-09-27 00:35:10 -0700 (Thu, 27 Sep 2007) | 1 line Change to LogRecord.__init__() to fix #1206. Note that archaic use of type(x) == types.DictType is because of keeping 1.5.2 compatibility. While this is much less relevant these days, there probably needs to be a separate commit for removing all archaic constructs at the same time. ........ r58288 | brett.cannon | 2007-09-30 12:45:10 -0700 (Sun, 30 Sep 2007) | 9 lines tuple.__repr__ did not consider a reference loop as it is not possible from Python code; but it is possible from C. object.__str__ had the issue of not expecting a type to doing something within it's tp_str implementation that could trigger an infinite recursion, but it could in C code.. Both found thanks to BaseException and how it handles its repr. Closes issue #1686386. Thanks to Thomas Herve for taking an initial stab at coming up with a solution. ........ r58289 | brett.cannon | 2007-09-30 13:37:19 -0700 (Sun, 30 Sep 2007) | 3 lines Fix error introduced by r58288; if a tuple is length 0 return its repr and don't worry about any self-referring tuples. ........ r58294 | facundo.batista | 2007-10-02 10:01:24 -0700 (Tue, 02 Oct 2007) | 11 lines Made the various is_* operations return booleans. This was discussed with Cawlishaw by mail, and he basically confirmed that to these is_* operations, there's no need to return Decimal(0) and Decimal(1) if the language supports the False and True booleans. Also added a few tests for the these functions in extra.decTest, since they are mostly untested (apart from the doctests). Thanks Mark Dickinson ........ r58295 | facundo.batista | 2007-10-02 11:21:18 -0700 (Tue, 02 Oct 2007) | 4 lines Added a class to store the digits of log(10), so that they can be made available when necessary without recomputing. Thanks Mark Dickinson ........ r58299 | mark.summerfield | 2007-10-03 01:53:21 -0700 (Wed, 03 Oct 2007) | 4 lines Added note in footnote about string comparisons about unicodedata.normalize(). ........ r58304 | raymond.hettinger | 2007-10-03 14:18:11 -0700 (Wed, 03 Oct 2007) | 1 line enumerate() is no longer bounded to using sequences shorter than LONG_MAX. The possibility of overflow was sending some newsgroup posters into a tizzy. ........ r58305 | raymond.hettinger | 2007-10-03 17:20:27 -0700 (Wed, 03 Oct 2007) | 1 line itertools.count() no longer limited to sys.maxint. ........ r58306 | kurt.kaiser | 2007-10-03 18:49:54 -0700 (Wed, 03 Oct 2007) | 3 lines Assume that the user knows when he wants to end the line; don't insert something he didn't select or complete. ........ r58307 | kurt.kaiser | 2007-10-03 19:07:50 -0700 (Wed, 03 Oct 2007) | 2 lines Remove unused theme that was causing a fault in p3k. ........ r58308 | kurt.kaiser | 2007-10-03 19:09:17 -0700 (Wed, 03 Oct 2007) | 2 lines Clean up EditorWindow close. ........ r58309 | kurt.kaiser | 2007-10-03 19:53:07 -0700 (Wed, 03 Oct 2007) | 7 lines textView cleanup. Patch 1718043 Tal Einat. M idlelib/EditorWindow.py M idlelib/aboutDialog.py M idlelib/textView.py M idlelib/NEWS.txt ........ r58310 | kurt.kaiser | 2007-10-03 20:11:12 -0700 (Wed, 03 Oct 2007) | 3 lines configDialog cleanup. Patch 1730217 Tal Einat. ........ r58311 | neal.norwitz | 2007-10-03 23:00:48 -0700 (Wed, 03 Oct 2007) | 4 lines Coverity #151: Remove deadcode. All this code already exists above starting at line 653. ........ r58325 | fred.drake | 2007-10-04 19:46:12 -0700 (Thu, 04 Oct 2007) | 1 line wrap lines to <80 characters before fixing errors ........ r58326 | raymond.hettinger | 2007-10-04 19:47:07 -0700 (Thu, 04 Oct 2007) | 6 lines Add __asdict__() to NamedTuple and refine the docs. Add maxlen support to deque() and fixup docs. Partially fix __reduce__(). The None as a third arg was no longer supported. Still needs work on __reduce__() to handle recursive inputs. ........ r58327 | fred.drake | 2007-10-04 19:48:32 -0700 (Thu, 04 Oct 2007) | 3 lines move descriptions of ac_(in|out)_buffer_size to the right place http://bugs.python.org/issue1053 ........ r58329 | neal.norwitz | 2007-10-04 20:39:17 -0700 (Thu, 04 Oct 2007) | 3 lines dict could be NULL, so we need to XDECREF. Fix a compiler warning about passing a PyTypeObject* instead of PyObject*. ........ r58330 | neal.norwitz | 2007-10-04 20:41:19 -0700 (Thu, 04 Oct 2007) | 2 lines Fix Coverity #158: Check the correct variable. ........ r58332 | neal.norwitz | 2007-10-04 22:01:38 -0700 (Thu, 04 Oct 2007) | 7 lines Fix Coverity #159. This code was broken if save() returned a negative number since i contained a boolean value and then we compared i < 0 which should never be true. Will backport (assuming it's necessary) ........ r58334 | neal.norwitz | 2007-10-04 22:29:17 -0700 (Thu, 04 Oct 2007) | 1 line Add a note about fixing some more warnings found by Coverity. ........ r58338 | raymond.hettinger | 2007-10-05 12:07:31 -0700 (Fri, 05 Oct 2007) | 1 line Restore BEGIN/END THREADS macros which were squashed in the previous checkin ........ r58343 | gregory.p.smith | 2007-10-06 00:48:10 -0700 (Sat, 06 Oct 2007) | 3 lines Stab in the dark attempt to fix the test_bsddb3 failure on sparc and S-390 ubuntu buildbots. ........ r58344 | gregory.p.smith | 2007-10-06 00:51:59 -0700 (Sat, 06 Oct 2007) | 2 lines Allows BerkeleyDB 4.6.x >= 4.6.21 for the bsddb module. ........ r58348 | gregory.p.smith | 2007-10-06 08:47:37 -0700 (Sat, 06 Oct 2007) | 3 lines Use the host the author likely meant in the first place. pop.gmail.com is reliable. gmail.org is someones personal domain. ........ r58351 | neal.norwitz | 2007-10-06 12:16:28 -0700 (Sat, 06 Oct 2007) | 3 lines Ensure that this test will pass even if another test left an unwritable TESTFN. Also use the safe unlink in test_support instead of rolling our own here. ........ r58368 | georg.brandl | 2007-10-08 00:50:24 -0700 (Mon, 08 Oct 2007) | 3 lines #1123: fix the docs for the str.split(None, sep) case. Also expand a few other methods' docs, which had more info in the deprecated string module docs. ........ r58369 | georg.brandl | 2007-10-08 01:06:05 -0700 (Mon, 08 Oct 2007) | 2 lines Update docstring of sched, also remove an unused assignment. ........ r58370 | raymond.hettinger | 2007-10-08 02:14:28 -0700 (Mon, 08 Oct 2007) | 5 lines Add comments to NamedTuple code. Let the field spec be either a string or a non-string sequence (suggested by Martin Blais with use cases). Improve the error message in the case of a SyntaxError (caused by a duplicate field name). ........ r58371 | raymond.hettinger | 2007-10-08 02:56:29 -0700 (Mon, 08 Oct 2007) | 1 line Missed a line in the docs ........ r58372 | raymond.hettinger | 2007-10-08 03:11:51 -0700 (Mon, 08 Oct 2007) | 1 line Better variable names ........ r58376 | georg.brandl | 2007-10-08 07:12:47 -0700 (Mon, 08 Oct 2007) | 3 lines #1199: docs for tp_as_{number,sequence,mapping}, by Amaury Forgeot d'Arc. No need to merge this to py3k! ........ r58380 | raymond.hettinger | 2007-10-08 14:26:58 -0700 (Mon, 08 Oct 2007) | 1 line Eliminate camelcase function name ........ r58381 | andrew.kuchling | 2007-10-08 16:23:03 -0700 (Mon, 08 Oct 2007) | 1 line Eliminate camelcase function name ........ r58382 | raymond.hettinger | 2007-10-08 18:36:23 -0700 (Mon, 08 Oct 2007) | 1 line Make the error messages more specific ........ r58384 | gregory.p.smith | 2007-10-08 23:02:21 -0700 (Mon, 08 Oct 2007) | 10 lines Splits Modules/_bsddb.c up into bsddb.h and _bsddb.c and adds a C API object available as bsddb.db.api. This is based on the patch submitted by Duncan Grisby here: http://sourceforge.net/tracker/index.php?func=detail&aid=1551895&group_id=13900&atid=313900 See this thread for additional info: http://sourceforge.net/mailarchive/forum.php?thread_name=E1GAVDK-0002rk-Iw%40apasphere.com&forum_name=pybsddb-users It also cleans up the code a little by removing some ifdef/endifs for python prior to 2.1 and for unsupported Berkeley DB <= 3.2. ........ r58385 | gregory.p.smith | 2007-10-08 23:50:43 -0700 (Mon, 08 Oct 2007) | 5 lines Fix a double free when positioning a database cursor to a non-existant string key (and probably a few other situations with string keys). This was reported with a patch as pybsddb sourceforge bug 1708868 by jjjhhhlll at gmail. ........ r58386 | gregory.p.smith | 2007-10-09 00:19:11 -0700 (Tue, 09 Oct 2007) | 3 lines Use the highest cPickle protocol in bsddb.dbshelve. This comes from sourceforge pybsddb patch 1551443 by w_barnes. ........ r58394 | gregory.p.smith | 2007-10-09 11:26:02 -0700 (Tue, 09 Oct 2007) | 2 lines remove another sleepycat reference ........ r58396 | kurt.kaiser | 2007-10-09 12:31:30 -0700 (Tue, 09 Oct 2007) | 3 lines Allow interrupt only when executing user code in subprocess Patch 1225 Tal Einat modified from IDLE-Spoon. ........ r58399 | brett.cannon | 2007-10-09 17:07:50 -0700 (Tue, 09 Oct 2007) | 5 lines Remove file-level typedefs that were inconsistently used throughout the file. Just move over to the public API names. Closes issue1238. ........ r58401 | raymond.hettinger | 2007-10-09 17:26:46 -0700 (Tue, 09 Oct 2007) | 1 line Accept Jim Jewett's api suggestion to use None instead of -1 to indicate unbounded deques. ........ r58403 | kurt.kaiser | 2007-10-09 17:55:40 -0700 (Tue, 09 Oct 2007) | 2 lines Allow cursor color change w/o restart. Patch 1725576 Tal Einat. ........ r58404 | kurt.kaiser | 2007-10-09 18:06:47 -0700 (Tue, 09 Oct 2007) | 2 lines show paste if > 80 columns. Patch 1659326 Tal Einat. ........ r58415 | thomas.heller | 2007-10-11 12:51:32 -0700 (Thu, 11 Oct 2007) | 5 lines On OS X, use os.uname() instead of gestalt.sysv(...) to get the operating system version. This allows to use ctypes when Python was configured with --disable-toolbox-glue. ........ r58419 | neal.norwitz | 2007-10-11 20:01:01 -0700 (Thu, 11 Oct 2007) | 1 line Get rid of warning about not being able to create an existing directory. ........ r58420 | neal.norwitz | 2007-10-11 20:01:30 -0700 (Thu, 11 Oct 2007) | 1 line Get rid of warnings on a bunch of platforms by using a proper prototype. ........ r58421 | neal.norwitz | 2007-10-11 20:01:54 -0700 (Thu, 11 Oct 2007) | 4 lines Get rid of compiler warning about retval being used (returned) without being initialized. (gcc warning and Coverity 202) ........ r58422 | neal.norwitz | 2007-10-11 20:03:23 -0700 (Thu, 11 Oct 2007) | 1 line Fix Coverity 168: Close the file before returning (exiting). ........ r58423 | neal.norwitz | 2007-10-11 20:04:18 -0700 (Thu, 11 Oct 2007) | 4 lines Fix Coverity 180: Don't overallocate. We don't need structs, but pointers. Also fix a memory leak. ........ r58424 | neal.norwitz | 2007-10-11 20:05:19 -0700 (Thu, 11 Oct 2007) | 5 lines Fix Coverity 185-186: If the passed in FILE is NULL, uninitialized memory would be accessed. Will backport. ........ r58425 | neal.norwitz | 2007-10-11 20:52:34 -0700 (Thu, 11 Oct 2007) | 1 line Get this module to compile with bsddb versions prior to 4.3 ........ r58430 | martin.v.loewis | 2007-10-12 01:56:52 -0700 (Fri, 12 Oct 2007) | 3 lines Bug #1216: Restore support for Visual Studio 2002. Will backport to 2.5. ........ r58433 | raymond.hettinger | 2007-10-12 10:53:11 -0700 (Fri, 12 Oct 2007) | 1 line Fix test of count.__repr__() to ignore the 'L' if the count is a long ........ r58434 | gregory.p.smith | 2007-10-12 11:44:06 -0700 (Fri, 12 Oct 2007) | 4 lines Fixes http://bugs.python.org/issue1233 - bsddb.dbshelve.DBShelf.append was useless due to inverted logic. Also adds a test case for RECNO dbs to test_dbshelve. ........ r58445 | georg.brandl | 2007-10-13 06:20:03 -0700 (Sat, 13 Oct 2007) | 2 lines Fix email example. ........ r58450 | gregory.p.smith | 2007-10-13 16:02:05 -0700 (Sat, 13 Oct 2007) | 2 lines Fix an uncollectable reference leak in bsddb.db.DBShelf.append ........ r58453 | neal.norwitz | 2007-10-13 17:18:40 -0700 (Sat, 13 Oct 2007) | 8 lines Let the O/S supply a port if none of the default ports can be used. This should make the tests more robust at the expense of allowing tests to be sloppier by not requiring them to cleanup after themselves. (It will legitamitely help when running two test suites simultaneously or if another process is already using one of the predefined ports.) Also simplifies (slightLy) the exception handling elsewhere. ........ r58459 | neal.norwitz | 2007-10-14 11:30:21 -0700 (Sun, 14 Oct 2007) | 2 lines Don't raise a string exception, they don't work anymore. ........ r58460 | neal.norwitz | 2007-10-14 11:40:37 -0700 (Sun, 14 Oct 2007) | 1 line Use unittest for assertions ........ r58468 | armin.rigo | 2007-10-15 00:48:35 -0700 (Mon, 15 Oct 2007) | 2 lines test_bigbits was not testing what it seemed to. ........ r58471 | guido.van.rossum | 2007-10-15 08:54:11 -0700 (Mon, 15 Oct 2007) | 3 lines Change a PyErr_Print() into a PyErr_Clear(), per discussion in issue 1031213. ........ r58500 | raymond.hettinger | 2007-10-16 12:18:30 -0700 (Tue, 16 Oct 2007) | 1 line Improve error messages ........ r58506 | raymond.hettinger | 2007-10-16 14:28:32 -0700 (Tue, 16 Oct 2007) | 1 line More docs, error messages, and tests ........ r58507 | andrew.kuchling | 2007-10-16 15:58:03 -0700 (Tue, 16 Oct 2007) | 1 line Add items ........ r58508 | brett.cannon | 2007-10-16 16:24:06 -0700 (Tue, 16 Oct 2007) | 3 lines Remove ``:const:`` notation on None in parameter list. Since the markup is not rendered for parameters it just showed up as ``:const:`None` `` in the output. ........ r58509 | brett.cannon | 2007-10-16 16:26:45 -0700 (Tue, 16 Oct 2007) | 3 lines Re-order some functions whose parameters differ between PyObject and const char * so that they are next to each other. ........ r58522 | armin.rigo | 2007-10-17 11:46:37 -0700 (Wed, 17 Oct 2007) | 5 lines Fix the overflow checking of list_repeat. Introduce overflow checking into list_inplace_repeat. Backport candidate, possibly. ........ r58530 | facundo.batista | 2007-10-17 20:16:03 -0700 (Wed, 17 Oct 2007) | 7 lines Issue #1580738. When HTTPConnection reads the whole stream with read(), it closes itself. When the stream is read in several calls to read(n), it should behave in the same way if HTTPConnection knows where the end of the stream is (through self.length). Added a test case for this behaviour. ........ r58531 | facundo.batista | 2007-10-17 20:44:48 -0700 (Wed, 17 Oct 2007) | 3 lines Issue 1289, just a typo. ........ r58532 | gregory.p.smith | 2007-10-18 00:56:54 -0700 (Thu, 18 Oct 2007) | 4 lines cleanup test_dbtables to use mkdtemp. cleanup dbtables to pass txn as a keyword argument whenever possible to avoid bugs and confusion. (dbtables.py line 447 self.db.get using txn as a non-keyword was an actual bug due to this) ........ r58533 | gregory.p.smith | 2007-10-18 01:34:20 -0700 (Thu, 18 Oct 2007) | 4 lines Fix a weird bug in dbtables: if it chose a random rowid string that contained NULL bytes it would cause the database all sorts of problems in the future leading to very strange random failures and corrupt dbtables.bsdTableDb dbs. ........ r58534 | gregory.p.smith | 2007-10-18 09:32:02 -0700 (Thu, 18 Oct 2007) | 3 lines A cleaner fix than the one committed last night. Generate random rowids that do not contain null bytes. ........ r58537 | gregory.p.smith | 2007-10-18 10:17:57 -0700 (Thu, 18 Oct 2007) | 2 lines mention bsddb fixes. ........ r58538 | raymond.hettinger | 2007-10-18 14:13:06 -0700 (Thu, 18 Oct 2007) | 1 line Remove useless warning ........ r58539 | gregory.p.smith | 2007-10-19 00:31:20 -0700 (Fri, 19 Oct 2007) | 2 lines squelch the warning that this test is supposed to trigger. ........ r58542 | georg.brandl | 2007-10-19 05:32:39 -0700 (Fri, 19 Oct 2007) | 2 lines Clarify wording for apply(). ........ r58544 | mark.summerfield | 2007-10-19 05:48:17 -0700 (Fri, 19 Oct 2007) | 3 lines Added a cross-ref to each other. ........ r58545 | georg.brandl | 2007-10-19 10:38:49 -0700 (Fri, 19 Oct 2007) | 2 lines #1284: "S" means "seen", not unread. ........ r58548 | thomas.heller | 2007-10-19 11:11:41 -0700 (Fri, 19 Oct 2007) | 4 lines Fix ctypes on 32-bit systems when Python is configured --with-system-ffi. See also https://bugs.launchpad.net/bugs/72505. Ported from release25-maint branch. ........ r58550 | facundo.batista | 2007-10-19 12:25:57 -0700 (Fri, 19 Oct 2007) | 8 lines The constructor from tuple was way too permissive: it allowed bad coefficient numbers, floats in the sign, and other details that generated directly the wrong number in the best case, or triggered misfunctionality in the alorithms. Test cases added for these issues. Thanks Mark Dickinson. ........ r58559 | georg.brandl | 2007-10-20 06:22:53 -0700 (Sat, 20 Oct 2007) | 2 lines Fix code being interpreted as a target. ........ r58561 | georg.brandl | 2007-10-20 06:36:24 -0700 (Sat, 20 Oct 2007) | 2 lines Document new "cmdoption" directive. ........ r58562 | georg.brandl | 2007-10-20 08:21:22 -0700 (Sat, 20 Oct 2007) | 2 lines Make a path more Unix-standardy. ........ r58564 | georg.brandl | 2007-10-20 10:51:39 -0700 (Sat, 20 Oct 2007) | 2 lines Document new directive "envvar". ........ r58567 | georg.brandl | 2007-10-20 11:08:14 -0700 (Sat, 20 Oct 2007) | 6 lines * Add new toplevel chapter, "Using Python." (how to install, configure and setup python on different platforms -- at least in theory.) * Move the Python on Mac docs in that chapter. * Add a new chapter about the command line invocation, by stargaming. ........ r58568 | georg.brandl | 2007-10-20 11:33:20 -0700 (Sat, 20 Oct 2007) | 2 lines Change title, for now. ........ r58569 | georg.brandl | 2007-10-20 11:39:25 -0700 (Sat, 20 Oct 2007) | 2 lines Add entry to ACKS. ........ r58570 | georg.brandl | 2007-10-20 12:05:45 -0700 (Sat, 20 Oct 2007) | 2 lines Clarify -E docs. ........ r58571 | georg.brandl | 2007-10-20 12:08:36 -0700 (Sat, 20 Oct 2007) | 2 lines Even more clarification. ........ r58572 | andrew.kuchling | 2007-10-20 12:25:37 -0700 (Sat, 20 Oct 2007) | 1 line Fix protocol name ........ r58573 | andrew.kuchling | 2007-10-20 12:35:18 -0700 (Sat, 20 Oct 2007) | 1 line Various items ........ r58574 | andrew.kuchling | 2007-10-20 12:39:35 -0700 (Sat, 20 Oct 2007) | 1 line Use correct header line ........ r58576 | armin.rigo | 2007-10-21 02:14:15 -0700 (Sun, 21 Oct 2007) | 3 lines Add a crasher for the long-standing issue with closing a file while another thread uses it. ........ r58577 | georg.brandl | 2007-10-21 03:01:56 -0700 (Sun, 21 Oct 2007) | 2 lines Remove duplicate crasher. ........ r58578 | georg.brandl | 2007-10-21 03:24:20 -0700 (Sun, 21 Oct 2007) | 2 lines Unify "byte code" to "bytecode". Also sprinkle :term: markup for it. ........ r58579 | georg.brandl | 2007-10-21 03:32:54 -0700 (Sun, 21 Oct 2007) | 2 lines Add markup to new function descriptions. ........ r58580 | georg.brandl | 2007-10-21 03:45:46 -0700 (Sun, 21 Oct 2007) | 2 lines Add :term:s for descriptors. ........ r58581 | georg.brandl | 2007-10-21 03:46:24 -0700 (Sun, 21 Oct 2007) | 2 lines Unify "file-descriptor" to "file descriptor". ........ r58582 | georg.brandl | 2007-10-21 03:52:38 -0700 (Sun, 21 Oct 2007) | 2 lines Add :term: for generators. ........ r58583 | georg.brandl | 2007-10-21 05:10:28 -0700 (Sun, 21 Oct 2007) | 2 lines Add :term:s for iterator. ........ r58584 | georg.brandl | 2007-10-21 05:15:05 -0700 (Sun, 21 Oct 2007) | 2 lines Add :term:s for "new-style class". ........ r58588 | neal.norwitz | 2007-10-21 21:47:54 -0700 (Sun, 21 Oct 2007) | 1 line Add Chris Monson so he can edit PEPs. ........ r58594 | guido.van.rossum | 2007-10-22 09:27:19 -0700 (Mon, 22 Oct 2007) | 4 lines Issue #1307, patch by Derek Shockey. When "MAIL" is received without args, an exception happens instead of sending a 501 syntax error response. ........ r58598 | travis.oliphant | 2007-10-22 19:40:56 -0700 (Mon, 22 Oct 2007) | 1 line Add phuang patch from Issue 708374 which adds offset parameter to mmap module. ........ r58601 | neal.norwitz | 2007-10-22 22:44:27 -0700 (Mon, 22 Oct 2007) | 2 lines Bug #1313, fix typo (wrong variable name) in example. ........ r58609 | georg.brandl | 2007-10-23 11:21:35 -0700 (Tue, 23 Oct 2007) | 2 lines Update Pygments version from externals. ........ r58618 | guido.van.rossum | 2007-10-23 12:25:41 -0700 (Tue, 23 Oct 2007) | 3 lines Issue 1307 by Derek Shockey, fox the same bug for RCPT. Neal: please backport! ........ r58620 | raymond.hettinger | 2007-10-23 13:37:41 -0700 (Tue, 23 Oct 2007) | 1 line Shorter name for namedtuple() ........ r58621 | andrew.kuchling | 2007-10-23 13:55:47 -0700 (Tue, 23 Oct 2007) | 1 line Update name ........ r58622 | raymond.hettinger | 2007-10-23 14:23:07 -0700 (Tue, 23 Oct 2007) | 1 line Fixup news entry ........ r58623 | raymond.hettinger | 2007-10-23 18:28:33 -0700 (Tue, 23 Oct 2007) | 1 line Optimize sum() for integer and float inputs. ........ r58624 | raymond.hettinger | 2007-10-23 19:05:51 -0700 (Tue, 23 Oct 2007) | 1 line Fixup error return and add support for intermixed ints and floats/ ........ r58628 | vinay.sajip | 2007-10-24 03:47:06 -0700 (Wed, 24 Oct 2007) | 1 line Bug #1321: Fixed logic error in TimedRotatingFileHandler.__init__() ........ r58641 | facundo.batista | 2007-10-24 12:11:08 -0700 (Wed, 24 Oct 2007) | 4 lines Issue 1290. CharacterData.__repr__ was constructing a string in response that keeped having a non-ascii character. ........ r58643 | thomas.heller | 2007-10-24 12:50:45 -0700 (Wed, 24 Oct 2007) | 1 line Added unittest for calling a function with paramflags (backport from py3k branch). ........ r58645 | matthias.klose | 2007-10-24 13:00:44 -0700 (Wed, 24 Oct 2007) | 2 lines - Build using system ffi library on arm*-linux*. ........ r58651 | georg.brandl | 2007-10-24 14:40:38 -0700 (Wed, 24 Oct 2007) | 2 lines Bug #1287: make os.environ.pop() work as expected. ........ r58652 | raymond.hettinger | 2007-10-24 19:26:58 -0700 (Wed, 24 Oct 2007) | 1 line Missing DECREFs ........ r58653 | matthias.klose | 2007-10-24 23:37:24 -0700 (Wed, 24 Oct 2007) | 2 lines - Build using system ffi library on arm*-linux*, pass --with-system-ffi to CONFIG_ARGS ........ r58655 | thomas.heller | 2007-10-25 12:47:32 -0700 (Thu, 25 Oct 2007) | 2 lines ffi_type_longdouble may be already #defined. See issue 1324. ........ r58656 | kurt.kaiser | 2007-10-25 15:43:45 -0700 (Thu, 25 Oct 2007) | 3 lines Correct an ancient bug in an unused path by removing that path: register() is now idempotent. ........ r58660 | kurt.kaiser | 2007-10-25 17:10:09 -0700 (Thu, 25 Oct 2007) | 4 lines 1. Add comments to provide top-level documentation. 2. Refactor to use more descriptive names. 3. Enhance tests in main(). ........ r58675 | georg.brandl | 2007-10-26 11:30:41 -0700 (Fri, 26 Oct 2007) | 2 lines Fix new pop() method on os.environ on ignorecase-platforms. ........ r58696 | neal.norwitz | 2007-10-27 15:32:21 -0700 (Sat, 27 Oct 2007) | 1 line Update URL for Pygments. 0.8.1 is no longer available ........ r58697 | hyeshik.chang | 2007-10-28 04:19:02 -0700 (Sun, 28 Oct 2007) | 3 lines - Add support for FreeBSD 8 which is recently forked from FreeBSD 7. - Regenerate IN module for most recent maintenance tree of FreeBSD 6 and 7. ........ r58698 | hyeshik.chang | 2007-10-28 05:38:09 -0700 (Sun, 28 Oct 2007) | 2 lines Enable platform-specific tweaks for FreeBSD 8 (exactly same to FreeBSD 7's yet) ........ r58700 | kurt.kaiser | 2007-10-28 12:03:59 -0700 (Sun, 28 Oct 2007) | 2 lines Add confirmation dialog before printing. Patch 1717170 Tal Einat. ........ r58706 | guido.van.rossum | 2007-10-29 13:52:45 -0700 (Mon, 29 Oct 2007) | 3 lines Patch 1353 by Jacob Winther. Add mp4 mapping to mimetypes.py. ........ r58709 | guido.van.rossum | 2007-10-29 15:15:05 -0700 (Mon, 29 Oct 2007) | 6 lines Backport fixes for the code that decodes octal escapes (and for PyString also hex escapes) -- this was reaching beyond the end of the input string buffer, even though it is not supposed to be \0-terminated. This has no visible effect but is clearly the correct thing to do. (In 3.0 it had a visible effect after removing ob_sstate from PyString.) ........ r58710 | kurt.kaiser | 2007-10-29 19:38:54 -0700 (Mon, 29 Oct 2007) | 7 lines check in Tal Einat's update to tabpage.py Patch 1612746 M configDialog.py M NEWS.txt AM tabbedpages.py ........ r58715 | georg.brandl | 2007-10-30 10:51:18 -0700 (Tue, 30 Oct 2007) | 2 lines Use correct markup. ........ r58716 | georg.brandl | 2007-10-30 10:57:12 -0700 (Tue, 30 Oct 2007) | 2 lines Make example about hiding None return values at the prompt clearer. ........ r58728 | neal.norwitz | 2007-10-30 23:33:20 -0700 (Tue, 30 Oct 2007) | 1 line Fix some compiler warnings for signed comparisons on Unix and Windows. ........ r58731 | martin.v.loewis | 2007-10-31 10:19:33 -0700 (Wed, 31 Oct 2007) | 2 lines Adding Christian Heimes. ........ r58737 | raymond.hettinger | 2007-10-31 14:57:58 -0700 (Wed, 31 Oct 2007) | 1 line Clarify the reasons why pickle is almost always better than marshal ........ r58739 | raymond.hettinger | 2007-10-31 15:15:49 -0700 (Wed, 31 Oct 2007) | 1 line Sets are marshalable. ........
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Code objects represent *byte-compiled* executable Python code, or :term:`bytecode`.
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The difference between a code object and a function object is that the function
object contains an explicit reference to the function's globals (the module in
which it was defined), while a code object contains no context; also the default
argument values are stored in the function object, not in the code object
(because they represent values calculated at run-time). Unlike function
objects, code objects are immutable and contain no references (directly or
indirectly) to mutable objects.
.. index::
single: co_argcount (code object attribute)
single: co_posonlyargcount (code object attribute)
single: co_kwonlyargcount (code object attribute)
single: co_code (code object attribute)
single: co_consts (code object attribute)
single: co_filename (code object attribute)
single: co_firstlineno (code object attribute)
single: co_flags (code object attribute)
single: co_lnotab (code object attribute)
single: co_name (code object attribute)
single: co_names (code object attribute)
single: co_nlocals (code object attribute)
single: co_stacksize (code object attribute)
single: co_varnames (code object attribute)
single: co_cellvars (code object attribute)
single: co_freevars (code object attribute)
single: co_qualname (code object attribute)
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Special read-only attributes: :attr:`co_name` gives the function name;
:attr:`co_qualname` gives the fully qualified function name;
:attr:`co_argcount` is the total number of positional arguments
(including positional-only arguments and arguments with default values);
:attr:`co_posonlyargcount` is the number of positional-only arguments
(including arguments with default values); :attr:`co_kwonlyargcount` is
the number of keyword-only arguments (including arguments with default
values); :attr:`co_nlocals` is the number of local variables used by the
function (including arguments); :attr:`co_varnames` is a tuple containing
the names of the local variables (starting with the argument names);
:attr:`co_cellvars` is a tuple containing the names of local variables
that are referenced by nested functions; :attr:`co_freevars` is a tuple
containing the names of free variables; :attr:`co_code` is a string
representing the sequence of bytecode instructions; :attr:`co_consts` is
a tuple containing the literals used by the bytecode; :attr:`co_names` is
a tuple containing the names used by the bytecode; :attr:`co_filename` is
the filename from which the code was compiled; :attr:`co_firstlineno` is
the first line number of the function; :attr:`co_lnotab` is a string
encoding the mapping from bytecode offsets to line numbers (for details
see the source code of the interpreter); :attr:`co_stacksize` is the
required stack size; :attr:`co_flags` is an integer encoding a number
of flags for the interpreter.
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.. index:: object: generator
The following flag bits are defined for :attr:`co_flags`: bit ``0x04`` is set if
the function uses the ``*arguments`` syntax to accept an arbitrary number of
positional arguments; bit ``0x08`` is set if the function uses the
``**keywords`` syntax to accept arbitrary keyword arguments; bit ``0x20`` is set
if the function is a generator.
Future feature declarations (``from __future__ import division``) also use bits
in :attr:`co_flags` to indicate whether a code object was compiled with a
particular feature enabled: bit ``0x2000`` is set if the function was compiled
with future division enabled; bits ``0x10`` and ``0x1000`` were used in earlier
versions of Python.
Other bits in :attr:`co_flags` are reserved for internal use.
.. index:: single: documentation string
If a code object represents a function, the first item in :attr:`co_consts` is
the documentation string of the function, or ``None`` if undefined.
.. method:: codeobject.co_positions()
Returns an iterable over the source code positions of each bytecode
instruction in the code object.
The iterator returns tuples containing the ``(start_line, end_line,
start_column, end_column)``. The *i-th* tuple corresponds to the
position of the source code that compiled to the *i-th* instruction.
Column information is 0-indexed utf-8 byte offsets on the given source
line.
This positional information can be missing. A non-exhaustive lists of
cases where this may happen:
- Running the interpreter with :option:`-X` ``no_debug_ranges``.
- Loading a pyc file compiled while using :option:`-X` ``no_debug_ranges``.
- Position tuples corresponding to artificial instructions.
- Line and column numbers that can't be represented due to
implementation specific limitations.
When this occurs, some or all of the tuple elements can be
:const:`None`.
.. versionadded:: 3.11
.. note::
This feature requires storing column positions in code objects which may
result in a small increase of disk usage of compiled Python files or
interpreter memory usage. To avoid storing the extra information and/or
deactivate printing the extra traceback information, the
:option:`-X` ``no_debug_ranges`` command line flag or the :envvar:`PYTHONNODEBUGRANGES`
environment variable can be used.
Merged revisions 74542,74544-74548,74550,74554-74555,74578,74588,74590,74603,74616-74618,74621 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74542 | georg.brandl | 2009-08-23 23:28:56 +0200 (So, 23 Aug 2009) | 1 line Restore alphabetic order. ........ r74544 | georg.brandl | 2009-08-24 19:12:30 +0200 (Mo, 24 Aug 2009) | 1 line #6775: fix python.org URLs in README. ........ r74545 | georg.brandl | 2009-08-24 19:14:29 +0200 (Mo, 24 Aug 2009) | 1 line #6772: mention utf-8 as utf8 alias. ........ r74546 | georg.brandl | 2009-08-24 19:20:40 +0200 (Mo, 24 Aug 2009) | 1 line #6725: spell "namespace" consistently. ........ r74547 | georg.brandl | 2009-08-24 19:22:05 +0200 (Mo, 24 Aug 2009) | 1 line #6718: fix example. ........ r74548 | georg.brandl | 2009-08-24 19:24:27 +0200 (Mo, 24 Aug 2009) | 1 line #6677: mention "deleting" as an alias for removing files. ........ r74550 | georg.brandl | 2009-08-24 19:48:40 +0200 (Mo, 24 Aug 2009) | 1 line #6677: note that rmdir only removes empty directories. ........ r74554 | georg.brandl | 2009-08-27 20:59:02 +0200 (Do, 27 Aug 2009) | 1 line Typo fix. ........ r74555 | georg.brandl | 2009-08-27 21:02:43 +0200 (Do, 27 Aug 2009) | 1 line #6787: reference fix. ........ r74578 | tarek.ziade | 2009-08-29 15:33:21 +0200 (Sa, 29 Aug 2009) | 1 line fixed #6801: symmetric_difference_update also accepts pipe ........ r74588 | georg.brandl | 2009-08-30 10:35:01 +0200 (So, 30 Aug 2009) | 1 line #6803: fix old name. ........ r74590 | georg.brandl | 2009-08-30 13:51:53 +0200 (So, 30 Aug 2009) | 1 line #6801: fix copy-paste oversight. ........ r74603 | georg.brandl | 2009-08-31 08:38:29 +0200 (Mo, 31 Aug 2009) | 1 line other -> others where multiple arguments are accepted. ........ r74616 | georg.brandl | 2009-09-01 09:46:26 +0200 (Di, 01 Sep 2009) | 1 line #6808: clarification. ........ r74617 | georg.brandl | 2009-09-01 09:53:37 +0200 (Di, 01 Sep 2009) | 1 line #6765: hint that log(x, base) is not very sophisticated. ........ r74618 | georg.brandl | 2009-09-01 10:00:47 +0200 (Di, 01 Sep 2009) | 1 line #6810: add a link to the section about frame objects instead of just a description where to find it. ........ r74621 | georg.brandl | 2009-09-01 10:06:03 +0200 (Di, 01 Sep 2009) | 1 line #6638: fix wrong parameter name and markup a class. ........
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.. _frame-objects:
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Frame objects
.. index:: object: frame
Frame objects represent execution frames. They may occur in traceback objects
(see below), and are also passed to registered trace functions.
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.. index::
single: f_back (frame attribute)
single: f_code (frame attribute)
single: f_globals (frame attribute)
single: f_locals (frame attribute)
single: f_lasti (frame attribute)
single: f_builtins (frame attribute)
Special read-only attributes: :attr:`f_back` is to the previous stack frame
(towards the caller), or ``None`` if this is the bottom stack frame;
:attr:`f_code` is the code object being executed in this frame; :attr:`f_locals`
is the dictionary used to look up local variables; :attr:`f_globals` is used for
global variables; :attr:`f_builtins` is used for built-in (intrinsic) names;
:attr:`f_lasti` gives the precise instruction (this is an index into the
bytecode string of the code object).
Accessing ``f_code`` raises an :ref:`auditing event <auditing>`
``object.__getattr__`` with arguments ``obj`` and ``"f_code"``.
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.. index::
single: f_trace (frame attribute)
single: f_trace_lines (frame attribute)
single: f_trace_opcodes (frame attribute)
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single: f_lineno (frame attribute)
Special writable attributes: :attr:`f_trace`, if not ``None``, is a function
called for various events during code execution (this is used by the debugger).
Normally an event is triggered for each new source line - this can be
disabled by setting :attr:`f_trace_lines` to :const:`False`.
Implementations *may* allow per-opcode events to be requested by setting
:attr:`f_trace_opcodes` to :const:`True`. Note that this may lead to
undefined interpreter behaviour if exceptions raised by the trace
function escape to the function being traced.
:attr:`f_lineno` is the current line number of the frame --- writing to this
from within a trace function jumps to the given line (only for the bottom-most
frame). A debugger can implement a Jump command (aka Set Next Statement)
by writing to f_lineno.
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Frame objects support one method:
.. method:: frame.clear()
This method clears all references to local variables held by the
frame. Also, if the frame belonged to a generator, the generator
is finalized. This helps break reference cycles involving frame
objects (for example when catching an exception and storing its
traceback for later use).
:exc:`RuntimeError` is raised if the frame is currently executing.
.. versionadded:: 3.4
.. _traceback-objects:
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Traceback objects
.. index::
object: traceback
pair: stack; trace
pair: exception; handler
pair: execution; stack
single: exc_info (in module sys)
single: last_traceback (in module sys)
single: sys.exc_info
single: sys.last_traceback
Traceback objects represent a stack trace of an exception. A traceback object
is implicitly created when an exception occurs, and may also be explicitly
created by calling :class:`types.TracebackType`.
For implicitly created tracebacks, when the search for an exception handler
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unwinds the execution stack, at each unwound level a traceback object is
inserted in front of the current traceback. When an exception handler is
entered, the stack trace is made available to the program. (See section
:ref:`try`.) It is accessible as the third item of the
tuple returned by ``sys.exc_info()``, and as the ``__traceback__`` attribute
of the caught exception.
When the program contains no suitable
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handler, the stack trace is written (nicely formatted) to the standard error
stream; if the interpreter is interactive, it is also made available to the user
as ``sys.last_traceback``.
For explicitly created tracebacks, it is up to the creator of the traceback
to determine how the ``tb_next`` attributes should be linked to form a
full stack trace.
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.. index::
single: tb_frame (traceback attribute)
single: tb_lineno (traceback attribute)
single: tb_lasti (traceback attribute)
statement: try
Special read-only attributes:
:attr:`tb_frame` points to the execution frame of the current level;
:attr:`tb_lineno` gives the line number where the exception occurred;
:attr:`tb_lasti` indicates the precise instruction.
The line number and last instruction in the traceback may differ from the
line number of its frame object if the exception occurred in a
:keyword:`try` statement with no matching except clause or with a
finally clause.
Accessing ``tb_frame`` raises an :ref:`auditing event <auditing>`
``object.__getattr__`` with arguments ``obj`` and ``"tb_frame"``.
.. index::
single: tb_next (traceback attribute)
Special writable attribute: :attr:`tb_next` is the next level in the stack
trace (towards the frame where the exception occurred), or ``None`` if
there is no next level.
.. versionchanged:: 3.7
Traceback objects can now be explicitly instantiated from Python code,
and the ``tb_next`` attribute of existing instances can be updated.
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Slice objects
.. index:: builtin: slice
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Slice objects are used to represent slices for :meth:`__getitem__`
methods. They are also created by the built-in :func:`slice` function.
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.. index::
single: start (slice object attribute)
single: stop (slice object attribute)
single: step (slice object attribute)
Special read-only attributes: :attr:`~slice.start` is the lower bound;
:attr:`~slice.stop` is the upper bound; :attr:`~slice.step` is the step
value; each is ``None`` if omitted. These attributes can have any type.
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Slice objects support one method:
.. method:: slice.indices(self, length)
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This method takes a single integer argument *length* and computes
information about the slice that the slice object would describe if
applied to a sequence of *length* items. It returns a tuple of three
integers; respectively these are the *start* and *stop* indices and the
*step* or stride length of the slice. Missing or out-of-bounds indices
are handled in a manner consistent with regular slices.
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Static method objects
Static method objects provide a way of defeating the transformation of function
objects to method objects described above. A static method object is a wrapper
around any other object, usually a user-defined method object. When a static
method object is retrieved from a class or a class instance, the object actually
returned is the wrapped object, which is not subject to any further
transformation. Static method objects are also callable. Static method
objects are created by the built-in :func:`staticmethod` constructor.
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Class method objects
A class method object, like a static method object, is a wrapper around another
object that alters the way in which that object is retrieved from classes and
class instances. The behaviour of class method objects upon such retrieval is
described above, under "User-defined methods". Class method objects are created
by the built-in :func:`classmethod` constructor.
.. _specialnames:
Special method names
====================
.. index::
pair: operator; overloading
single: __getitem__() (mapping object method)
A class can implement certain operations that are invoked by special syntax
(such as arithmetic operations or subscripting and slicing) by defining methods
with special names. This is Python's approach to :dfn:`operator overloading`,
allowing classes to define their own behavior with respect to language
operators. For instance, if a class defines a method named :meth:`__getitem__`,
and ``x`` is an instance of this class, then ``x[i]`` is roughly equivalent
to ``type(x).__getitem__(x, i)``. Except where mentioned, attempts to execute an
operation raise an exception when no appropriate method is defined (typically
:exc:`AttributeError` or :exc:`TypeError`).
Setting a special method to ``None`` indicates that the corresponding
operation is not available. For example, if a class sets
:meth:`__iter__` to ``None``, the class is not iterable, so calling
:func:`iter` on its instances will raise a :exc:`TypeError` (without
falling back to :meth:`__getitem__`). [#]_
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When implementing a class that emulates any built-in type, it is important that
the emulation only be implemented to the degree that it makes sense for the
object being modelled. For example, some sequences may work well with retrieval
of individual elements, but extracting a slice may not make sense. (One example
of this is the :class:`~xml.dom.NodeList` interface in the W3C's Document
Object Model.)
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.. _customization:
Basic customization
-------------------
.. method:: object.__new__(cls[, ...])
Merged revisions 67531-67532,67538,67553-67554,67556-67557,67571,67574-67575,67579-67580,67591,67597,67608,67631 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r67531 | georg.brandl | 2008-12-04 19:54:05 +0100 (Thu, 04 Dec 2008) | 2 lines Add reference to enumerate() to indices example. ........ r67532 | georg.brandl | 2008-12-04 19:59:16 +0100 (Thu, 04 Dec 2008) | 2 lines Add another heapq example. ........ r67538 | georg.brandl | 2008-12-04 22:28:16 +0100 (Thu, 04 Dec 2008) | 2 lines Clarification to avoid confusing output with file descriptors. ........ r67553 | georg.brandl | 2008-12-05 08:49:49 +0100 (Fri, 05 Dec 2008) | 2 lines #4408: document regex.groups. ........ r67554 | georg.brandl | 2008-12-05 08:52:26 +0100 (Fri, 05 Dec 2008) | 2 lines #4409: fix asterisks looking like footnotes. ........ r67556 | georg.brandl | 2008-12-05 09:02:17 +0100 (Fri, 05 Dec 2008) | 2 lines #4441: improve doc for os.open() flags. ........ r67557 | georg.brandl | 2008-12-05 09:06:57 +0100 (Fri, 05 Dec 2008) | 2 lines Add an index entry for "subclassing immutable types". ........ r67571 | georg.brandl | 2008-12-05 10:13:45 +0100 (Fri, 05 Dec 2008) | 2 lines Use markup. ........ r67574 | georg.brandl | 2008-12-05 10:25:32 +0100 (Fri, 05 Dec 2008) | 2 lines #4441 followup: Add link to open() docs for Windows. ........ r67575 | georg.brandl | 2008-12-05 12:34:51 +0100 (Fri, 05 Dec 2008) | 2 lines #4544: add `dedent` to textwrap.__all__. ........ r67579 | georg.brandl | 2008-12-05 16:29:39 +0100 (Fri, 05 Dec 2008) | 2 lines #4517: add "special method" glossary entry and clarify when __getattribute__ is bypassed. ........ r67580 | georg.brandl | 2008-12-05 16:32:29 +0100 (Fri, 05 Dec 2008) | 2 lines #4478: document that copyfile() can raise Error. ........ r67591 | georg.brandl | 2008-12-05 19:00:06 +0100 (Fri, 05 Dec 2008) | 2 lines Followup to #4511: add link from decorator glossary entry to definition. ........ r67597 | georg.brandl | 2008-12-05 20:03:19 +0100 (Fri, 05 Dec 2008) | 2 lines Remove confusing sentence part. ........ r67608 | georg.brandl | 2008-12-06 12:57:12 +0100 (Sat, 06 Dec 2008) | 2 lines Follow-up to #4488: document PIPE and STDOUT properly. ........ r67631 | georg.brandl | 2008-12-07 12:54:07 +0100 (Sun, 07 Dec 2008) | 2 lines Add link to the favicon to the docs. ........
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.. index:: pair: subclassing; immutable types
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Called to create a new instance of class *cls*. :meth:`__new__` is a static
method (special-cased so you need not declare it as such) that takes the class
of which an instance was requested as its first argument. The remaining
arguments are those passed to the object constructor expression (the call to the
class). The return value of :meth:`__new__` should be the new object instance
(usually an instance of *cls*).
Typical implementations create a new instance of the class by invoking the
superclass's :meth:`__new__` method using ``super().__new__(cls[, ...])``
with appropriate arguments and then modifying the newly-created instance
as necessary before returning it.
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If :meth:`__new__` is invoked during object construction and it returns an
instance or subclass of *cls*, then the new instances :meth:`__init__` method
will be invoked like ``__init__(self[, ...])``, where *self* is the new instance
and the remaining arguments are the same as were passed to the object constructor.
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If :meth:`__new__` does not return an instance of *cls*, then the new instance's
:meth:`__init__` method will not be invoked.
:meth:`__new__` is intended mainly to allow subclasses of immutable types (like
Merged revisions 59822-59841 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59822 | georg.brandl | 2008-01-07 17:43:47 +0100 (Mon, 07 Jan 2008) | 2 lines Restore "somenamedtuple" as the "class" for named tuple attrs. ........ r59824 | georg.brandl | 2008-01-07 18:09:35 +0100 (Mon, 07 Jan 2008) | 2 lines Patch #602345 by Neal Norwitz and me: add -B option and PYTHONDONTWRITEBYTECODE envvar to skip writing bytecode. ........ r59827 | georg.brandl | 2008-01-07 18:25:53 +0100 (Mon, 07 Jan 2008) | 2 lines patch #1668: clarify envvar docs; rename THREADDEBUG to PYTHONTHREADDEBUG. ........ r59830 | georg.brandl | 2008-01-07 19:16:36 +0100 (Mon, 07 Jan 2008) | 2 lines Make Python compile with --disable-unicode. ........ r59831 | georg.brandl | 2008-01-07 19:23:27 +0100 (Mon, 07 Jan 2008) | 2 lines Restructure urllib doc structure. ........ r59833 | georg.brandl | 2008-01-07 19:41:34 +0100 (Mon, 07 Jan 2008) | 2 lines Fix #define ordering. ........ r59834 | georg.brandl | 2008-01-07 19:47:44 +0100 (Mon, 07 Jan 2008) | 2 lines #467924, patch by Alan McIntyre: Add ZipFile.extract and ZipFile.extractall. ........ r59835 | raymond.hettinger | 2008-01-07 19:52:19 +0100 (Mon, 07 Jan 2008) | 1 line Fix inconsistent title levels -- it made the whole doc build crash horribly. ........ r59836 | georg.brandl | 2008-01-07 19:57:03 +0100 (Mon, 07 Jan 2008) | 2 lines Fix two further doc build warnings. ........ r59837 | georg.brandl | 2008-01-07 20:17:10 +0100 (Mon, 07 Jan 2008) | 2 lines Clarify metaclass docs and add example. ........ r59838 | vinay.sajip | 2008-01-07 20:40:10 +0100 (Mon, 07 Jan 2008) | 1 line Added section about adding contextual information to log output. ........ r59839 | christian.heimes | 2008-01-07 20:58:41 +0100 (Mon, 07 Jan 2008) | 1 line Fixed indention problem that caused the second TIPC test to run on systems without TIPC ........ r59840 | raymond.hettinger | 2008-01-07 21:07:38 +0100 (Mon, 07 Jan 2008) | 1 line Cleanup named tuple subclassing example. ........
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int, str, or tuple) to customize instance creation. It is also commonly
overridden in custom metaclasses in order to customize class creation.
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.. method:: object.__init__(self[, ...])
.. index:: pair: class; constructor
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Called after the instance has been created (by :meth:`__new__`), but before
it is returned to the caller. The arguments are those passed to the
class constructor expression. If a base class has an :meth:`__init__`
method, the derived class's :meth:`__init__` method, if any, must explicitly
call it to ensure proper initialization of the base class part of the
instance; for example: ``super().__init__([args...])``.
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Because :meth:`__new__` and :meth:`__init__` work together in constructing
objects (:meth:`__new__` to create it, and :meth:`__init__` to customize it),
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no non-``None`` value may be returned by :meth:`__init__`; doing so will
cause a :exc:`TypeError` to be raised at runtime.
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.. method:: object.__del__(self)
.. index::
single: destructor
single: finalizer
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statement: del
Called when the instance is about to be destroyed. This is also called a
finalizer or (improperly) a destructor. If a base class has a
:meth:`__del__` method, the derived class's :meth:`__del__` method,
if any, must explicitly call it to ensure proper deletion of the base
class part of the instance.
It is possible (though not recommended!) for the :meth:`__del__` method
to postpone destruction of the instance by creating a new reference to
it. This is called object *resurrection*. It is implementation-dependent
whether :meth:`__del__` is called a second time when a resurrected object
is about to be destroyed; the current :term:`CPython` implementation
only calls it once.
It is not guaranteed that :meth:`__del__` methods are called for objects
that still exist when the interpreter exits.
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.. note::
``del x`` doesn't directly call ``x.__del__()`` --- the former decrements
the reference count for ``x`` by one, and the latter is only called when
``x``'s reference count reaches zero.
.. impl-detail::
It is possible for a reference cycle to prevent the reference count
of an object from going to zero. In this case, the cycle will be
later detected and deleted by the :term:`cyclic garbage collector
<garbage collection>`. A common cause of reference cycles is when
an exception has been caught in a local variable. The frame's
locals then reference the exception, which references its own
traceback, which references the locals of all frames caught in the
traceback.
.. seealso::
Documentation for the :mod:`gc` module.
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.. warning::
Due to the precarious circumstances under which :meth:`__del__` methods are
invoked, exceptions that occur during their execution are ignored, and a warning
is printed to ``sys.stderr`` instead. In particular:
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* :meth:`__del__` can be invoked when arbitrary code is being executed,
including from any arbitrary thread. If :meth:`__del__` needs to take
a lock or invoke any other blocking resource, it may deadlock as
the resource may already be taken by the code that gets interrupted
to execute :meth:`__del__`.
* :meth:`__del__` can be executed during interpreter shutdown. As a
consequence, the global variables it needs to access (including other
modules) may already have been deleted or set to ``None``. Python
guarantees that globals whose name begins with a single underscore
are deleted from their module before other globals are deleted; if
no other references to such globals exist, this may help in assuring
that imported modules are still available at the time when the
:meth:`__del__` method is called.
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.. index::
single: repr() (built-in function); __repr__() (object method)
.. method:: object.__repr__(self)
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Called by the :func:`repr` built-in function to compute the "official" string
representation of an object. If at all possible, this should look like a
valid Python expression that could be used to recreate an object with the
same value (given an appropriate environment). If this is not possible, a
string of the form ``<...some useful description...>`` should be returned.
The return value must be a string object. If a class defines :meth:`__repr__`
but not :meth:`__str__`, then :meth:`__repr__` is also used when an
"informal" string representation of instances of that class is required.
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This is typically used for debugging, so it is important that the representation
is information-rich and unambiguous.
.. index::
single: string; __str__() (object method)
single: format() (built-in function); __str__() (object method)
single: print() (built-in function); __str__() (object method)
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.. method:: object.__str__(self)
Called by :func:`str(object) <str>` and the built-in functions
:func:`format` and :func:`print` to compute the "informal" or nicely
printable string representation of an object. The return value must be a
:ref:`string <textseq>` object.
This method differs from :meth:`object.__repr__` in that there is no
expectation that :meth:`__str__` return a valid Python expression: a more
convenient or concise representation can be used.
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The default implementation defined by the built-in type :class:`object`
calls :meth:`object.__repr__`.
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.. XXX what about subclasses of string?
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.. method:: object.__bytes__(self)
.. index:: builtin: bytes
Called by :ref:`bytes <func-bytes>` to compute a byte-string representation
of an object. This should return a :class:`bytes` object.
.. index::
single: string; __format__() (object method)
pair: string; conversion
builtin: print
.. method:: object.__format__(self, format_spec)
Called by the :func:`format` built-in function,
and by extension, evaluation of :ref:`formatted string literals
<f-strings>` and the :meth:`str.format` method, to produce a "formatted"
string representation of an object. The *format_spec* argument is
a string that contains a description of the formatting options desired.
The interpretation of the *format_spec* argument is up to the type
implementing :meth:`__format__`, however most classes will either
delegate formatting to one of the built-in types, or use a similar
formatting option syntax.
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See :ref:`formatspec` for a description of the standard formatting syntax.
The return value must be a string object.
.. versionchanged:: 3.4
The __format__ method of ``object`` itself raises a :exc:`TypeError`
if passed any non-empty string.
.. versionchanged:: 3.7
``object.__format__(x, '')`` is now equivalent to ``str(x)`` rather
than ``format(str(x), '')``.
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.. _richcmpfuncs:
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.. method:: object.__lt__(self, other)
object.__le__(self, other)
object.__eq__(self, other)
object.__ne__(self, other)
object.__gt__(self, other)
object.__ge__(self, other)
Merged revisions 58742-58816 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r58745 | georg.brandl | 2007-11-01 10:19:33 -0700 (Thu, 01 Nov 2007) | 2 lines #1364: os.lstat is available on Windows too, as an alias to os.stat. ........ r58750 | christian.heimes | 2007-11-01 12:48:10 -0700 (Thu, 01 Nov 2007) | 1 line Backport of import tests for bug http://bugs.python.org/issue1293 and bug http://bugs.python.org/issue1342 ........ r58751 | christian.heimes | 2007-11-01 13:11:06 -0700 (Thu, 01 Nov 2007) | 1 line Removed non ASCII text from test as requested by Guido. Sorry :/ ........ r58753 | georg.brandl | 2007-11-01 13:37:02 -0700 (Thu, 01 Nov 2007) | 2 lines Fix markup glitch. ........ r58757 | gregory.p.smith | 2007-11-01 14:08:14 -0700 (Thu, 01 Nov 2007) | 4 lines Fix bug introduced in revision 58385. Database keys could no longer have NULL bytes in them. Replace the errant strdup with a malloc+memcpy. Adds a unit test for the correct behavior. ........ r58758 | gregory.p.smith | 2007-11-01 14:15:36 -0700 (Thu, 01 Nov 2007) | 3 lines Undo revision 58533 58534 fixes. Those were a workaround for a problem introduced by 58385. ........ r58759 | gregory.p.smith | 2007-11-01 14:17:47 -0700 (Thu, 01 Nov 2007) | 2 lines false "fix" undone as correct problem was found and fixed. ........ r58765 | mark.summerfield | 2007-11-02 01:24:59 -0700 (Fri, 02 Nov 2007) | 3 lines Added more file-handling related cross-references. ........ r58766 | nick.coghlan | 2007-11-02 03:09:12 -0700 (Fri, 02 Nov 2007) | 1 line Fix for bug 1705170 - contextmanager swallowing StopIteration (2.5 backport candidate) ........ r58784 | thomas.heller | 2007-11-02 12:10:24 -0700 (Fri, 02 Nov 2007) | 4 lines Issue #1292: On alpha, arm, ppc, and s390 linux systems the --with-system-ffi configure option defaults to "yes" because the bundled libffi sources are too old. ........ r58785 | thomas.heller | 2007-11-02 12:11:23 -0700 (Fri, 02 Nov 2007) | 1 line Enable the full ctypes c_longdouble tests again. ........ r58796 | georg.brandl | 2007-11-02 13:06:17 -0700 (Fri, 02 Nov 2007) | 4 lines Make "hashable" a glossary entry and clarify docs on __cmp__, __eq__ and __hash__. I hope the concept of hashability is better understandable now. Thanks to Tim Hatch for pointing out the flaws here. ........
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.. index::
single: comparisons
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These are the so-called "rich comparison" methods. The correspondence between
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operator symbols and method names is as follows: ``x<y`` calls ``x.__lt__(y)``,
``x<=y`` calls ``x.__le__(y)``, ``x==y`` calls ``x.__eq__(y)``, ``x!=y`` calls
``x.__ne__(y)``, ``x>y`` calls ``x.__gt__(y)``, and ``x>=y`` calls
``x.__ge__(y)``.
A rich comparison method may return the singleton ``NotImplemented`` if it does
not implement the operation for a given pair of arguments. By convention,
``False`` and ``True`` are returned for a successful comparison. However, these
methods can return any value, so if the comparison operator is used in a Boolean
context (e.g., in the condition of an ``if`` statement), Python will call
:func:`bool` on the value to determine if the result is true or false.
By default, ``object`` implements :meth:`__eq__` by using ``is``, returning
``NotImplemented`` in the case of a false comparison:
``True if x is y else NotImplemented``. For :meth:`__ne__`, by default it
delegates to :meth:`__eq__` and inverts the result unless it is
``NotImplemented``. There are no other implied relationships among the
comparison operators or default implementations; for example, the truth of
``(x<y or x==y)`` does not imply ``x<=y``. To automatically generate ordering
operations from a single root operation, see :func:`functools.total_ordering`.
See the paragraph on :meth:`__hash__` for
Merged revisions 58742-58816 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r58745 | georg.brandl | 2007-11-01 10:19:33 -0700 (Thu, 01 Nov 2007) | 2 lines #1364: os.lstat is available on Windows too, as an alias to os.stat. ........ r58750 | christian.heimes | 2007-11-01 12:48:10 -0700 (Thu, 01 Nov 2007) | 1 line Backport of import tests for bug http://bugs.python.org/issue1293 and bug http://bugs.python.org/issue1342 ........ r58751 | christian.heimes | 2007-11-01 13:11:06 -0700 (Thu, 01 Nov 2007) | 1 line Removed non ASCII text from test as requested by Guido. Sorry :/ ........ r58753 | georg.brandl | 2007-11-01 13:37:02 -0700 (Thu, 01 Nov 2007) | 2 lines Fix markup glitch. ........ r58757 | gregory.p.smith | 2007-11-01 14:08:14 -0700 (Thu, 01 Nov 2007) | 4 lines Fix bug introduced in revision 58385. Database keys could no longer have NULL bytes in them. Replace the errant strdup with a malloc+memcpy. Adds a unit test for the correct behavior. ........ r58758 | gregory.p.smith | 2007-11-01 14:15:36 -0700 (Thu, 01 Nov 2007) | 3 lines Undo revision 58533 58534 fixes. Those were a workaround for a problem introduced by 58385. ........ r58759 | gregory.p.smith | 2007-11-01 14:17:47 -0700 (Thu, 01 Nov 2007) | 2 lines false "fix" undone as correct problem was found and fixed. ........ r58765 | mark.summerfield | 2007-11-02 01:24:59 -0700 (Fri, 02 Nov 2007) | 3 lines Added more file-handling related cross-references. ........ r58766 | nick.coghlan | 2007-11-02 03:09:12 -0700 (Fri, 02 Nov 2007) | 1 line Fix for bug 1705170 - contextmanager swallowing StopIteration (2.5 backport candidate) ........ r58784 | thomas.heller | 2007-11-02 12:10:24 -0700 (Fri, 02 Nov 2007) | 4 lines Issue #1292: On alpha, arm, ppc, and s390 linux systems the --with-system-ffi configure option defaults to "yes" because the bundled libffi sources are too old. ........ r58785 | thomas.heller | 2007-11-02 12:11:23 -0700 (Fri, 02 Nov 2007) | 1 line Enable the full ctypes c_longdouble tests again. ........ r58796 | georg.brandl | 2007-11-02 13:06:17 -0700 (Fri, 02 Nov 2007) | 4 lines Make "hashable" a glossary entry and clarify docs on __cmp__, __eq__ and __hash__. I hope the concept of hashability is better understandable now. Thanks to Tim Hatch for pointing out the flaws here. ........
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some important notes on creating :term:`hashable` objects which support
custom comparison operations and are usable as dictionary keys.
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Merged revisions 58742-58816 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r58745 | georg.brandl | 2007-11-01 10:19:33 -0700 (Thu, 01 Nov 2007) | 2 lines #1364: os.lstat is available on Windows too, as an alias to os.stat. ........ r58750 | christian.heimes | 2007-11-01 12:48:10 -0700 (Thu, 01 Nov 2007) | 1 line Backport of import tests for bug http://bugs.python.org/issue1293 and bug http://bugs.python.org/issue1342 ........ r58751 | christian.heimes | 2007-11-01 13:11:06 -0700 (Thu, 01 Nov 2007) | 1 line Removed non ASCII text from test as requested by Guido. Sorry :/ ........ r58753 | georg.brandl | 2007-11-01 13:37:02 -0700 (Thu, 01 Nov 2007) | 2 lines Fix markup glitch. ........ r58757 | gregory.p.smith | 2007-11-01 14:08:14 -0700 (Thu, 01 Nov 2007) | 4 lines Fix bug introduced in revision 58385. Database keys could no longer have NULL bytes in them. Replace the errant strdup with a malloc+memcpy. Adds a unit test for the correct behavior. ........ r58758 | gregory.p.smith | 2007-11-01 14:15:36 -0700 (Thu, 01 Nov 2007) | 3 lines Undo revision 58533 58534 fixes. Those were a workaround for a problem introduced by 58385. ........ r58759 | gregory.p.smith | 2007-11-01 14:17:47 -0700 (Thu, 01 Nov 2007) | 2 lines false "fix" undone as correct problem was found and fixed. ........ r58765 | mark.summerfield | 2007-11-02 01:24:59 -0700 (Fri, 02 Nov 2007) | 3 lines Added more file-handling related cross-references. ........ r58766 | nick.coghlan | 2007-11-02 03:09:12 -0700 (Fri, 02 Nov 2007) | 1 line Fix for bug 1705170 - contextmanager swallowing StopIteration (2.5 backport candidate) ........ r58784 | thomas.heller | 2007-11-02 12:10:24 -0700 (Fri, 02 Nov 2007) | 4 lines Issue #1292: On alpha, arm, ppc, and s390 linux systems the --with-system-ffi configure option defaults to "yes" because the bundled libffi sources are too old. ........ r58785 | thomas.heller | 2007-11-02 12:11:23 -0700 (Fri, 02 Nov 2007) | 1 line Enable the full ctypes c_longdouble tests again. ........ r58796 | georg.brandl | 2007-11-02 13:06:17 -0700 (Fri, 02 Nov 2007) | 4 lines Make "hashable" a glossary entry and clarify docs on __cmp__, __eq__ and __hash__. I hope the concept of hashability is better understandable now. Thanks to Tim Hatch for pointing out the flaws here. ........
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There are no swapped-argument versions of these methods (to be used when the
left argument does not support the operation but the right argument does);
rather, :meth:`__lt__` and :meth:`__gt__` are each other's reflection,
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:meth:`__le__` and :meth:`__ge__` are each other's reflection, and
:meth:`__eq__` and :meth:`__ne__` are their own reflection.
If the operands are of different types, and right operand's type is
a direct or indirect subclass of the left operand's type,
the reflected method of the right operand has priority, otherwise
the left operand's method has priority. Virtual subclassing is
not considered.
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.. method:: object.__hash__(self)
.. index::
object: dictionary
builtin: hash
Called by built-in function :func:`hash` and for operations on members of
hashed collections including :class:`set`, :class:`frozenset`, and
:class:`dict`. :meth:`__hash__` should return an integer. The only required
property is that objects which compare equal have the same hash value; it is
advised to mix together the hash values of the components of the object that
also play a part in comparison of objects by packing them into a tuple and
hashing the tuple. Example::
def __hash__(self):
return hash((self.name, self.nick, self.color))
.. note::
:func:`hash` truncates the value returned from an object's custom
:meth:`__hash__` method to the size of a :c:type:`Py_ssize_t`. This is
typically 8 bytes on 64-bit builds and 4 bytes on 32-bit builds. If an
object's :meth:`__hash__` must interoperate on builds of different bit
sizes, be sure to check the width on all supported builds. An easy way
to do this is with
``python -c "import sys; print(sys.hash_info.width)"``.
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If a class does not define an :meth:`__eq__` method it should not define a
:meth:`__hash__` operation either; if it defines :meth:`__eq__` but not
:meth:`__hash__`, its instances will not be usable as items in hashable
collections. If a class defines mutable objects and implements an
:meth:`__eq__` method, it should not implement :meth:`__hash__`, since the
implementation of hashable collections requires that a key's hash value is
immutable (if the object's hash value changes, it will be in the wrong hash
bucket).
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User-defined classes have :meth:`__eq__` and :meth:`__hash__` methods
by default; with them, all objects compare unequal (except with themselves)
and ``x.__hash__()`` returns an appropriate value such that ``x == y``
implies both that ``x is y`` and ``hash(x) == hash(y)``.
A class that overrides :meth:`__eq__` and does not define :meth:`__hash__`
will have its :meth:`__hash__` implicitly set to ``None``. When the
:meth:`__hash__` method of a class is ``None``, instances of the class will
raise an appropriate :exc:`TypeError` when a program attempts to retrieve
their hash value, and will also be correctly identified as unhashable when
checking ``isinstance(obj, collections.abc.Hashable)``.
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If a class that overrides :meth:`__eq__` needs to retain the implementation
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of :meth:`__hash__` from a parent class, the interpreter must be told this
explicitly by setting ``__hash__ = <ParentClass>.__hash__``.
If a class that does not override :meth:`__eq__` wishes to suppress hash
support, it should include ``__hash__ = None`` in the class definition.
A class which defines its own :meth:`__hash__` that explicitly raises
a :exc:`TypeError` would be incorrectly identified as hashable by
an ``isinstance(obj, collections.abc.Hashable)`` call.
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.. note::
By default, the :meth:`__hash__` values of str and bytes objects are
"salted" with an unpredictable random value. Although they
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remain constant within an individual Python process, they are not
predictable between repeated invocations of Python.
This is intended to provide protection against a denial-of-service caused
by carefully-chosen inputs that exploit the worst case performance of a
dict insertion, O(n^2) complexity. See
http://www.ocert.org/advisories/ocert-2011-003.html for details.
Changing hash values affects the iteration order of sets.
Python has never made guarantees about this ordering
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(and it typically varies between 32-bit and 64-bit builds).
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See also :envvar:`PYTHONHASHSEED`.
.. versionchanged:: 3.3
Hash randomization is enabled by default.
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.. method:: object.__bool__(self)
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.. index:: single: __len__() (mapping object method)
Merged revisions 70342,70385-70387,70389-70390,70392-70393,70395,70400,70405-70406,70418,70438,70464,70468 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r70342 | georg.brandl | 2009-03-13 14:03:58 -0500 (Fri, 13 Mar 2009) | 1 line #5486: typos. ........ r70385 | benjamin.peterson | 2009-03-15 09:38:55 -0500 (Sun, 15 Mar 2009) | 1 line fix tuple.index() error message #5495 ........ r70386 | georg.brandl | 2009-03-15 16:32:06 -0500 (Sun, 15 Mar 2009) | 1 line #5496: fix docstring of lookup(). ........ r70387 | georg.brandl | 2009-03-15 16:37:16 -0500 (Sun, 15 Mar 2009) | 1 line #5493: clarify __nonzero__ docs. ........ r70389 | georg.brandl | 2009-03-15 16:43:38 -0500 (Sun, 15 Mar 2009) | 1 line Fix a small nit in the error message if bool() falls back on __len__ and it returns the wrong type: it would tell the user that __nonzero__ should return bool or int. ........ r70390 | georg.brandl | 2009-03-15 16:44:43 -0500 (Sun, 15 Mar 2009) | 1 line #5491: clarify nested() semantics. ........ r70392 | georg.brandl | 2009-03-15 16:46:00 -0500 (Sun, 15 Mar 2009) | 1 line #5488: add missing struct member. ........ r70393 | georg.brandl | 2009-03-15 16:47:42 -0500 (Sun, 15 Mar 2009) | 1 line #5478: fix copy-paste oversight in function signature. ........ r70395 | georg.brandl | 2009-03-15 16:51:48 -0500 (Sun, 15 Mar 2009) | 1 line #5276: document IDLESTARTUP and .Idle.py. ........ r70400 | georg.brandl | 2009-03-15 16:59:37 -0500 (Sun, 15 Mar 2009) | 3 lines Fix markup in re docs and give a mail address in regex howto, so that the recommendation to send suggestions to the author can be followed. ........ r70405 | georg.brandl | 2009-03-15 17:11:07 -0500 (Sun, 15 Mar 2009) | 7 lines Move the previously local import of threading to module level. This is cleaner and avoids lockups in obscure cases where a Queue is instantiated while the import lock is already held by another thread. OKed by Tim Peters. ........ r70406 | hirokazu.yamamoto | 2009-03-15 17:43:14 -0500 (Sun, 15 Mar 2009) | 1 line Added skip for old MSVC. ........ r70418 | georg.brandl | 2009-03-16 14:42:03 -0500 (Mon, 16 Mar 2009) | 1 line Add token markup. ........ r70438 | benjamin.peterson | 2009-03-17 15:29:51 -0500 (Tue, 17 Mar 2009) | 1 line I thought this was begging for an example ........ r70464 | benjamin.peterson | 2009-03-18 15:58:09 -0500 (Wed, 18 Mar 2009) | 1 line a much better example ........ r70468 | benjamin.peterson | 2009-03-18 22:04:31 -0500 (Wed, 18 Mar 2009) | 1 line close files after comparing them ........
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Called to implement truth value testing and the built-in operation
``bool()``; should return ``False`` or ``True``. When this method is not
defined, :meth:`__len__` is called, if it is defined, and the object is
considered true if its result is nonzero. If a class defines neither
:meth:`__len__` nor :meth:`__bool__`, all its instances are considered
true.
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.. _attribute-access:
Customizing attribute access
----------------------------
The following methods can be defined to customize the meaning of attribute
access (use of, assignment to, or deletion of ``x.name``) for class instances.
.. XXX explain how descriptors interfere here!
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.. method:: object.__getattr__(self, name)
Called when the default attribute access fails with an :exc:`AttributeError`
(either :meth:`__getattribute__` raises an :exc:`AttributeError` because
*name* is not an instance attribute or an attribute in the class tree
for ``self``; or :meth:`__get__` of a *name* property raises
:exc:`AttributeError`). This method should either return the (computed)
attribute value or raise an :exc:`AttributeError` exception.
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Note that if the attribute is found through the normal mechanism,
:meth:`__getattr__` is not called. (This is an intentional asymmetry between
:meth:`__getattr__` and :meth:`__setattr__`.) This is done both for efficiency
reasons and because otherwise :meth:`__getattr__` would have no way to access
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other attributes of the instance. Note that at least for instance variables,
you can fake total control by not inserting any values in the instance attribute
dictionary (but instead inserting them in another object). See the
:meth:`__getattribute__` method below for a way to actually get total control
over attribute access.
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.. method:: object.__getattribute__(self, name)
Called unconditionally to implement attribute accesses for instances of the
class. If the class also defines :meth:`__getattr__`, the latter will not be
called unless :meth:`__getattribute__` either calls it explicitly or raises an
:exc:`AttributeError`. This method should return the (computed) attribute value
or raise an :exc:`AttributeError` exception. In order to avoid infinite
recursion in this method, its implementation should always call the base class
method with the same name to access any attributes it needs, for example,
``object.__getattribute__(self, name)``.
.. note::
This method may still be bypassed when looking up special methods as the
result of implicit invocation via language syntax or built-in functions.
See :ref:`special-lookup`.
.. audit-event:: object.__getattr__ obj,name object.__getattribute__
For certain sensitive attribute accesses, raises an
:ref:`auditing event <auditing>` ``object.__getattr__`` with arguments
``obj`` and ``name``.
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.. method:: object.__setattr__(self, name, value)
Called when an attribute assignment is attempted. This is called instead of
the normal mechanism (i.e. store the value in the instance dictionary).
*name* is the attribute name, *value* is the value to be assigned to it.
If :meth:`__setattr__` wants to assign to an instance attribute, it should
call the base class method with the same name, for example,
``object.__setattr__(self, name, value)``.
.. audit-event:: object.__setattr__ obj,name,value object.__setattr__
For certain sensitive attribute assignments, raises an
:ref:`auditing event <auditing>` ``object.__setattr__`` with arguments
``obj``, ``name``, ``value``.
.. method:: object.__delattr__(self, name)
Like :meth:`__setattr__` but for attribute deletion instead of assignment. This
should only be implemented if ``del obj.name`` is meaningful for the object.
.. audit-event:: object.__delattr__ obj,name object.__delattr__
For certain sensitive attribute deletions, raises an
:ref:`auditing event <auditing>` ``object.__delattr__`` with arguments
``obj`` and ``name``.
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.. method:: object.__dir__(self)
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Called when :func:`dir` is called on the object. A sequence must be
returned. :func:`dir` converts the returned sequence to a list and sorts it.
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Customizing module attribute access
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. index::
single: __getattr__ (module attribute)
single: __dir__ (module attribute)
single: __class__ (module attribute)
Special names ``__getattr__`` and ``__dir__`` can be also used to customize
access to module attributes. The ``__getattr__`` function at the module level
should accept one argument which is the name of an attribute and return the
computed value or raise an :exc:`AttributeError`. If an attribute is
not found on a module object through the normal lookup, i.e.
:meth:`object.__getattribute__`, then ``__getattr__`` is searched in
the module ``__dict__`` before raising an :exc:`AttributeError`. If found,
it is called with the attribute name and the result is returned.
The ``__dir__`` function should accept no arguments, and return a sequence of
strings that represents the names accessible on module. If present, this
function overrides the standard :func:`dir` search on a module.
For a more fine grained customization of the module behavior (setting
attributes, properties, etc.), one can set the ``__class__`` attribute of
a module object to a subclass of :class:`types.ModuleType`. For example::
import sys
from types import ModuleType
class VerboseModule(ModuleType):
def __repr__(self):
return f'Verbose {self.__name__}'
def __setattr__(self, attr, value):
print(f'Setting {attr}...')
super().__setattr__(attr, value)
sys.modules[__name__].__class__ = VerboseModule
.. note::
Defining module ``__getattr__`` and setting module ``__class__`` only
affect lookups made using the attribute access syntax -- directly accessing
the module globals (whether by code within the module, or via a reference
to the module's globals dictionary) is unaffected.
.. versionchanged:: 3.5
``__class__`` module attribute is now writable.
.. versionadded:: 3.7
``__getattr__`` and ``__dir__`` module attributes.
.. seealso::
:pep:`562` - Module __getattr__ and __dir__
Describes the ``__getattr__`` and ``__dir__`` functions on modules.
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.. _descriptors:
Implementing Descriptors
^^^^^^^^^^^^^^^^^^^^^^^^
The following methods only apply when an instance of the class containing the
method (a so-called *descriptor* class) appears in an *owner* class (the
descriptor must be in either the owner's class dictionary or in the class
dictionary for one of its parents). In the examples below, "the attribute"
refers to the attribute whose name is the key of the property in the owner
class' :attr:`~object.__dict__`.
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.. method:: object.__get__(self, instance, owner=None)
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Called to get the attribute of the owner class (class attribute access) or
of an instance of that class (instance attribute access). The optional
*owner* argument is the owner class, while *instance* is the instance that
the attribute was accessed through, or ``None`` when the attribute is
accessed through the *owner*.
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This method should return the computed attribute value or raise an
:exc:`AttributeError` exception.
:PEP:`252` specifies that :meth:`__get__` is callable with one or two
arguments. Python's own built-in descriptors support this specification;
however, it is likely that some third-party tools have descriptors
that require both arguments. Python's own :meth:`__getattribute__`
implementation always passes in both arguments whether they are required
or not.
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.. method:: object.__set__(self, instance, value)
Called to set the attribute on an instance *instance* of the owner class to a
new value, *value*.
Note, adding :meth:`__set__` or :meth:`__delete__` changes the kind of
descriptor to a "data descriptor". See :ref:`descriptor-invocation` for
more details.
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.. method:: object.__delete__(self, instance)
Called to delete the attribute on an instance *instance* of the owner class.
.. method:: object.__set_name__(self, owner, name)
Called at the time the owning class *owner* is created. The
descriptor has been assigned to *name*.
.. note::
:meth:`__set_name__` is only called implicitly as part of the
:class:`type` constructor, so it will need to be called explicitly with
the appropriate parameters when a descriptor is added to a class after
initial creation::
class A:
pass
descr = custom_descriptor()
A.attr = descr
descr.__set_name__(A, 'attr')
See :ref:`class-object-creation` for more details.
.. versionadded:: 3.6
The attribute :attr:`__objclass__` is interpreted by the :mod:`inspect` module
as specifying the class where this object was defined (setting this
appropriately can assist in runtime introspection of dynamic class attributes).
For callables, it may indicate that an instance of the given type (or a
subclass) is expected or required as the first positional argument (for example,
CPython sets this attribute for unbound methods that are implemented in C).
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.. _descriptor-invocation:
Invoking Descriptors
^^^^^^^^^^^^^^^^^^^^
In general, a descriptor is an object attribute with "binding behavior", one
whose attribute access has been overridden by methods in the descriptor
protocol: :meth:`__get__`, :meth:`__set__`, and :meth:`__delete__`. If any of
those methods are defined for an object, it is said to be a descriptor.
The default behavior for attribute access is to get, set, or delete the
attribute from an object's dictionary. For instance, ``a.x`` has a lookup chain
starting with ``a.__dict__['x']``, then ``type(a).__dict__['x']``, and
continuing through the base classes of ``type(a)`` excluding metaclasses.
However, if the looked-up value is an object defining one of the descriptor
methods, then Python may override the default behavior and invoke the descriptor
method instead. Where this occurs in the precedence chain depends on which
descriptor methods were defined and how they were called.
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The starting point for descriptor invocation is a binding, ``a.x``. How the
arguments are assembled depends on ``a``:
Direct Call
The simplest and least common call is when user code directly invokes a
descriptor method: ``x.__get__(a)``.
Instance Binding
If binding to an object instance, ``a.x`` is transformed into the call:
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``type(a).__dict__['x'].__get__(a, type(a))``.
Class Binding
If binding to a class, ``A.x`` is transformed into the call:
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``A.__dict__['x'].__get__(None, A)``.
Super Binding
If ``a`` is an instance of :class:`super`, then the binding ``super(B, obj).m()``
searches ``obj.__class__.__mro__`` for the base class ``A``
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immediately preceding ``B`` and then invokes the descriptor with the call:
``A.__dict__['m'].__get__(obj, obj.__class__)``.
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For instance bindings, the precedence of descriptor invocation depends on
Merged revisions 77484,77487,77561,77570,77593,77603,77608,77667,77702-77703,77739,77858,77887,77889 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r77484 | skip.montanaro | 2010-01-13 19:12:34 -0600 (Wed, 13 Jan 2010) | 4 lines Update PyEval_EvalFrame to PyEval_EvalFrameEx. This looks to have been done partially before. Also add a comment describing how this might have to work with different versions of the interpreter. ........ r77487 | ezio.melotti | 2010-01-14 05:34:10 -0600 (Thu, 14 Jan 2010) | 1 line Fixed typo ........ r77561 | georg.brandl | 2010-01-17 02:42:30 -0600 (Sun, 17 Jan 2010) | 1 line #7699: improve datetime docs: straightforward linking to strftime/strptime section, mark classmethods as such. ........ r77570 | georg.brandl | 2010-01-17 06:14:42 -0600 (Sun, 17 Jan 2010) | 1 line Add note about usage of STRINGLIB_EMPTY. ........ r77593 | georg.brandl | 2010-01-17 17:33:53 -0600 (Sun, 17 Jan 2010) | 1 line Fix internal reference. ........ r77603 | benjamin.peterson | 2010-01-18 17:07:56 -0600 (Mon, 18 Jan 2010) | 8 lines data descriptors do not override the class dictionary if __get__ is not defined Adjust documentation and add a test to verify this behavior. See http://mail.python.org/pipermail/python-dev/2010-January/095637.html for discussion. ........ r77608 | gregory.p.smith | 2010-01-19 02:19:03 -0600 (Tue, 19 Jan 2010) | 6 lines Do not compile stubs for the sha2 series hashes in the openssl hashlib module when the openssl version is too old to support them. That leads both compiled code bloat and to unittests attempting to test implementations that don't exist for comparison purposes on such platforms. ........ r77667 | mark.dickinson | 2010-01-21 12:32:27 -0600 (Thu, 21 Jan 2010) | 1 line Add two more test_strtod test values. ........ r77702 | georg.brandl | 2010-01-23 02:43:31 -0600 (Sat, 23 Jan 2010) | 1 line #7762: fix refcount annotation of PyUnicode_Tailmatch(). ........ r77703 | georg.brandl | 2010-01-23 02:47:54 -0600 (Sat, 23 Jan 2010) | 1 line #7725: fix referencing issue. ........ r77739 | benjamin.peterson | 2010-01-24 21:52:52 -0600 (Sun, 24 Jan 2010) | 1 line mention from_float() in error message ........ r77858 | georg.brandl | 2010-01-30 11:57:48 -0600 (Sat, 30 Jan 2010) | 1 line #7802: fix invalid example (heh). ........ r77887 | georg.brandl | 2010-01-31 12:51:49 -0600 (Sun, 31 Jan 2010) | 5 lines Fix-up ftplib documentation: move exception descriptions to toplevel, not inside a class remove attribution in "versionadded" spell and grammar check docstring of FTP_TLS ........ r77889 | michael.foord | 2010-01-31 13:59:26 -0600 (Sun, 31 Jan 2010) | 1 line Minor modification to unittest documentation. ........
2010-02-02 22:35:45 -04:00
which descriptor methods are defined. A descriptor can define any combination
of :meth:`__get__`, :meth:`__set__` and :meth:`__delete__`. If it does not
define :meth:`__get__`, then accessing the attribute will return the descriptor
object itself unless there is a value in the object's instance dictionary. If
the descriptor defines :meth:`__set__` and/or :meth:`__delete__`, it is a data
descriptor; if it defines neither, it is a non-data descriptor. Normally, data
descriptors define both :meth:`__get__` and :meth:`__set__`, while non-data
descriptors have just the :meth:`__get__` method. Data descriptors with
:meth:`__get__` and :meth:`__set__` (and/or :meth:`__delete__`) defined always override a redefinition in an
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instance dictionary. In contrast, non-data descriptors can be overridden by
Merged revisions 77484,77487,77561,77570,77593,77603,77608,77667,77702-77703,77739,77858,77887,77889 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r77484 | skip.montanaro | 2010-01-13 19:12:34 -0600 (Wed, 13 Jan 2010) | 4 lines Update PyEval_EvalFrame to PyEval_EvalFrameEx. This looks to have been done partially before. Also add a comment describing how this might have to work with different versions of the interpreter. ........ r77487 | ezio.melotti | 2010-01-14 05:34:10 -0600 (Thu, 14 Jan 2010) | 1 line Fixed typo ........ r77561 | georg.brandl | 2010-01-17 02:42:30 -0600 (Sun, 17 Jan 2010) | 1 line #7699: improve datetime docs: straightforward linking to strftime/strptime section, mark classmethods as such. ........ r77570 | georg.brandl | 2010-01-17 06:14:42 -0600 (Sun, 17 Jan 2010) | 1 line Add note about usage of STRINGLIB_EMPTY. ........ r77593 | georg.brandl | 2010-01-17 17:33:53 -0600 (Sun, 17 Jan 2010) | 1 line Fix internal reference. ........ r77603 | benjamin.peterson | 2010-01-18 17:07:56 -0600 (Mon, 18 Jan 2010) | 8 lines data descriptors do not override the class dictionary if __get__ is not defined Adjust documentation and add a test to verify this behavior. See http://mail.python.org/pipermail/python-dev/2010-January/095637.html for discussion. ........ r77608 | gregory.p.smith | 2010-01-19 02:19:03 -0600 (Tue, 19 Jan 2010) | 6 lines Do not compile stubs for the sha2 series hashes in the openssl hashlib module when the openssl version is too old to support them. That leads both compiled code bloat and to unittests attempting to test implementations that don't exist for comparison purposes on such platforms. ........ r77667 | mark.dickinson | 2010-01-21 12:32:27 -0600 (Thu, 21 Jan 2010) | 1 line Add two more test_strtod test values. ........ r77702 | georg.brandl | 2010-01-23 02:43:31 -0600 (Sat, 23 Jan 2010) | 1 line #7762: fix refcount annotation of PyUnicode_Tailmatch(). ........ r77703 | georg.brandl | 2010-01-23 02:47:54 -0600 (Sat, 23 Jan 2010) | 1 line #7725: fix referencing issue. ........ r77739 | benjamin.peterson | 2010-01-24 21:52:52 -0600 (Sun, 24 Jan 2010) | 1 line mention from_float() in error message ........ r77858 | georg.brandl | 2010-01-30 11:57:48 -0600 (Sat, 30 Jan 2010) | 1 line #7802: fix invalid example (heh). ........ r77887 | georg.brandl | 2010-01-31 12:51:49 -0600 (Sun, 31 Jan 2010) | 5 lines Fix-up ftplib documentation: move exception descriptions to toplevel, not inside a class remove attribution in "versionadded" spell and grammar check docstring of FTP_TLS ........ r77889 | michael.foord | 2010-01-31 13:59:26 -0600 (Sun, 31 Jan 2010) | 1 line Minor modification to unittest documentation. ........
2010-02-02 22:35:45 -04:00
instances.
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Python methods (including :func:`staticmethod` and :func:`classmethod`) are
implemented as non-data descriptors. Accordingly, instances can redefine and
override methods. This allows individual instances to acquire behaviors that
differ from other instances of the same class.
The :func:`property` function is implemented as a data descriptor. Accordingly,
instances cannot override the behavior of a property.
.. _slots:
__slots__
^^^^^^^^^
*__slots__* allow us to explicitly declare data members (like
properties) and deny the creation of *__dict__* and *__weakref__*
(unless explicitly declared in *__slots__* or available in a parent.)
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The space saved over using *__dict__* can be significant.
Attribute lookup speed can be significantly improved as well.
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.. data:: object.__slots__
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This class variable can be assigned a string, iterable, or sequence of
strings with variable names used by instances. *__slots__* reserves space
for the declared variables and prevents the automatic creation of *__dict__*
and *__weakref__* for each instance.
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Notes on using *__slots__*
""""""""""""""""""""""""""
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* When inheriting from a class without *__slots__*, the *__dict__* and
*__weakref__* attribute of the instances will always be accessible.
Merged revisions 65012,65035,65037-65040,65048,65057,65077,65091-65095,65097-65099,65127-65128,65131,65133-65136,65139,65149-65151,65155,65158-65159,65176-65178,65183-65184,65187-65190,65192,65194 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r65012 | jesse.noller | 2008-07-16 15:24:06 +0200 (Wed, 16 Jul 2008) | 2 lines Apply patch for issue 3090: ARCHFLAGS parsing incorrect ........ r65035 | georg.brandl | 2008-07-16 23:19:28 +0200 (Wed, 16 Jul 2008) | 2 lines #3045: fix pydoc behavior for TEMP path with spaces. ........ r65037 | georg.brandl | 2008-07-16 23:31:41 +0200 (Wed, 16 Jul 2008) | 2 lines #1608818: errno can get set by every call to readdir(). ........ r65038 | georg.brandl | 2008-07-17 00:04:20 +0200 (Thu, 17 Jul 2008) | 2 lines #3305: self->stream can be NULL. ........ r65039 | georg.brandl | 2008-07-17 00:09:17 +0200 (Thu, 17 Jul 2008) | 2 lines #3345: fix docstring. ........ r65040 | georg.brandl | 2008-07-17 00:33:18 +0200 (Thu, 17 Jul 2008) | 2 lines #3312: fix two sqlite3 crashes. ........ r65048 | georg.brandl | 2008-07-17 01:35:54 +0200 (Thu, 17 Jul 2008) | 2 lines #3388: add a paragraph about using "with" for file objects. ........ r65057 | gregory.p.smith | 2008-07-17 05:13:05 +0200 (Thu, 17 Jul 2008) | 2 lines news note for r63052 ........ r65077 | jesse.noller | 2008-07-17 23:01:05 +0200 (Thu, 17 Jul 2008) | 3 lines Fix issue 3395, update _debugInfo to be _debug_info ........ r65091 | ronald.oussoren | 2008-07-18 07:48:03 +0200 (Fri, 18 Jul 2008) | 2 lines Last bit of a fix for issue3381 (addon for my patch in r65061) ........ r65092 | vinay.sajip | 2008-07-18 10:59:06 +0200 (Fri, 18 Jul 2008) | 1 line Issue #3389: Allow resolving dotted names for handlers in logging configuration files. Thanks to Philip Jenvey for the patch. ........ r65093 | vinay.sajip | 2008-07-18 11:00:00 +0200 (Fri, 18 Jul 2008) | 1 line Issue #3389: Allow resolving dotted names for handlers in logging configuration files. Thanks to Philip Jenvey for the patch. ........ r65094 | vinay.sajip | 2008-07-18 11:00:35 +0200 (Fri, 18 Jul 2008) | 1 line Issue #3389: Allow resolving dotted names for handlers in logging configuration files. Thanks to Philip Jenvey for the patch. ........ r65095 | vinay.sajip | 2008-07-18 11:01:10 +0200 (Fri, 18 Jul 2008) | 1 line Issue #3389: Allow resolving dotted names for handlers in logging configuration files. Thanks to Philip Jenvey for the patch. ........ r65097 | georg.brandl | 2008-07-18 12:20:59 +0200 (Fri, 18 Jul 2008) | 2 lines Remove duplicate entry in __all__. ........ r65098 | georg.brandl | 2008-07-18 12:29:30 +0200 (Fri, 18 Jul 2008) | 2 lines Correct attribute name. ........ r65099 | georg.brandl | 2008-07-18 13:15:06 +0200 (Fri, 18 Jul 2008) | 3 lines Document the different meaning of precision for {:f} and {:g}. Also document how inf and nan are formatted. #3404. ........ r65127 | raymond.hettinger | 2008-07-19 02:42:03 +0200 (Sat, 19 Jul 2008) | 1 line Improve accuracy of gamma test function ........ r65128 | raymond.hettinger | 2008-07-19 02:43:00 +0200 (Sat, 19 Jul 2008) | 1 line Add recipe to the itertools docs. ........ r65131 | georg.brandl | 2008-07-19 12:08:55 +0200 (Sat, 19 Jul 2008) | 2 lines #3378: in case of no memory, don't leak even more memory. :) ........ r65133 | georg.brandl | 2008-07-19 14:39:10 +0200 (Sat, 19 Jul 2008) | 3 lines #3302: fix segfaults when passing None for arguments that can't be NULL for the C functions. ........ r65134 | georg.brandl | 2008-07-19 14:46:12 +0200 (Sat, 19 Jul 2008) | 2 lines #3303: fix crash with invalid Py_DECREF in strcoll(). ........ r65135 | georg.brandl | 2008-07-19 15:00:22 +0200 (Sat, 19 Jul 2008) | 3 lines #3319: don't raise ZeroDivisionError if number of rounds is so low that benchtime is zero. ........ r65136 | georg.brandl | 2008-07-19 15:09:42 +0200 (Sat, 19 Jul 2008) | 3 lines #3323: mention that if inheriting from a class without __slots__, the subclass will have a __dict__ available too. ........ r65139 | georg.brandl | 2008-07-19 15:48:44 +0200 (Sat, 19 Jul 2008) | 2 lines Add ordering info for findall and finditer. ........ r65149 | raymond.hettinger | 2008-07-20 01:21:57 +0200 (Sun, 20 Jul 2008) | 1 line Fix compress() recipe in docs to use itertools. ........ r65150 | raymond.hettinger | 2008-07-20 01:58:47 +0200 (Sun, 20 Jul 2008) | 1 line Clean-up itertools docs and recipes. ........ r65151 | gregory.p.smith | 2008-07-20 02:22:08 +0200 (Sun, 20 Jul 2008) | 9 lines fix issue3120 - don't truncate handles on 64-bit Windows. This is still messy, realistically PC/_subprocess.c should never cast pointers to python numbers and back at all. I don't have a 64-bit windows build environment because microsoft apparently thinks that should cost money. Time to watch the buildbots. It builds and passes tests on 32-bit windows. ........ r65155 | georg.brandl | 2008-07-20 13:50:29 +0200 (Sun, 20 Jul 2008) | 2 lines #926501: add info where to put the docstring. ........ r65158 | neal.norwitz | 2008-07-20 21:35:23 +0200 (Sun, 20 Jul 2008) | 1 line Fix a couple of names in error messages that were wrong ........ r65159 | neal.norwitz | 2008-07-20 22:39:36 +0200 (Sun, 20 Jul 2008) | 1 line Fix misspeeld method name (negative) ........ r65176 | amaury.forgeotdarc | 2008-07-21 23:36:24 +0200 (Mon, 21 Jul 2008) | 4 lines Increment version number in NEWS file, and move items that were added after 2.6b2. (I thought there was a script to automate this kind of updates) ........ r65177 | amaury.forgeotdarc | 2008-07-22 00:00:38 +0200 (Tue, 22 Jul 2008) | 5 lines Issue2378: pdb would delete free variables when stepping into a class statement. The problem was introduced by r53954, the correction is to restore the symmetry between PyFrame_FastToLocals and PyFrame_LocalsToFast ........ r65178 | benjamin.peterson | 2008-07-22 00:05:34 +0200 (Tue, 22 Jul 2008) | 1 line don't use assert statement ........ r65183 | ronald.oussoren | 2008-07-22 09:06:00 +0200 (Tue, 22 Jul 2008) | 2 lines Fix buglet in fix for issue3381 ........ r65184 | ronald.oussoren | 2008-07-22 09:06:33 +0200 (Tue, 22 Jul 2008) | 2 lines Fix build issue on OSX 10.4, somehow this wasn't committed before. ........ r65187 | raymond.hettinger | 2008-07-22 20:54:02 +0200 (Tue, 22 Jul 2008) | 1 line Remove out-of-date section on Exact/Inexact. ........ r65188 | raymond.hettinger | 2008-07-22 21:00:47 +0200 (Tue, 22 Jul 2008) | 1 line Tuples now have both count() and index(). ........ r65189 | raymond.hettinger | 2008-07-22 21:03:05 +0200 (Tue, 22 Jul 2008) | 1 line Fix credits for math.sum() ........ r65190 | raymond.hettinger | 2008-07-22 21:18:50 +0200 (Tue, 22 Jul 2008) | 1 line One more attribution. ........ r65192 | benjamin.peterson | 2008-07-23 01:44:37 +0200 (Wed, 23 Jul 2008) | 1 line remove unneeded import ........ r65194 | benjamin.peterson | 2008-07-23 15:25:06 +0200 (Wed, 23 Jul 2008) | 1 line use isinstance ........
2008-07-23 13:10:53 -03:00
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* Without a *__dict__* variable, instances cannot be assigned new variables not
listed in the *__slots__* definition. Attempts to assign to an unlisted
variable name raises :exc:`AttributeError`. If dynamic assignment of new
variables is desired, then add ``'__dict__'`` to the sequence of strings in
the *__slots__* declaration.
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* Without a *__weakref__* variable for each instance, classes defining
*__slots__* do not support weak references to its instances. If weak reference
support is needed, then add ``'__weakref__'`` to the sequence of strings in the
*__slots__* declaration.
* *__slots__* are implemented at the class level by creating descriptors
(:ref:`descriptors`) for each variable name. As a result, class attributes
cannot be used to set default values for instance variables defined by
*__slots__*; otherwise, the class attribute would overwrite the descriptor
assignment.
* The action of a *__slots__* declaration is not limited to the class
where it is defined. *__slots__* declared in parents are available in
child classes. However, child subclasses will get a *__dict__* and
*__weakref__* unless they also define *__slots__* (which should only
contain names of any *additional* slots).
Merged revisions 75365,75394,75402-75403,75418,75459,75484,75592-75596,75600,75602-75607,75610-75613,75616-75617,75623,75627,75640,75647,75696,75795 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r75365 | georg.brandl | 2009-10-11 22:16:16 +0200 (So, 11 Okt 2009) | 1 line Fix broken links found by "make linkcheck". scipy.org seems to be done right now, so I could not verify links going there. ........ r75394 | georg.brandl | 2009-10-13 20:10:59 +0200 (Di, 13 Okt 2009) | 1 line Fix markup. ........ r75402 | georg.brandl | 2009-10-14 17:51:48 +0200 (Mi, 14 Okt 2009) | 1 line #7125: fix typo. ........ r75403 | georg.brandl | 2009-10-14 17:57:46 +0200 (Mi, 14 Okt 2009) | 1 line #7126: os.environ changes *do* take effect in subprocesses started with os.system(). ........ r75418 | georg.brandl | 2009-10-14 20:48:32 +0200 (Mi, 14 Okt 2009) | 1 line #7116: str.join() takes an iterable. ........ r75459 | georg.brandl | 2009-10-17 10:57:43 +0200 (Sa, 17 Okt 2009) | 1 line Fix refleaks in _ctypes PyCSimpleType_New, which fixes the refleak seen in test___all__. ........ r75484 | georg.brandl | 2009-10-18 09:58:12 +0200 (So, 18 Okt 2009) | 1 line Fix missing word. ........ r75592 | georg.brandl | 2009-10-22 09:05:48 +0200 (Do, 22 Okt 2009) | 1 line Fix punctuation. ........ r75593 | georg.brandl | 2009-10-22 09:06:49 +0200 (Do, 22 Okt 2009) | 1 line Revert unintended change. ........ r75594 | georg.brandl | 2009-10-22 09:56:02 +0200 (Do, 22 Okt 2009) | 1 line Fix markup. ........ r75595 | georg.brandl | 2009-10-22 09:56:56 +0200 (Do, 22 Okt 2009) | 1 line Fix duplicate target. ........ r75596 | georg.brandl | 2009-10-22 10:05:04 +0200 (Do, 22 Okt 2009) | 1 line Add a new directive marking up implementation details and start using it. ........ r75600 | georg.brandl | 2009-10-22 13:01:46 +0200 (Do, 22 Okt 2009) | 1 line Make it more robust. ........ r75602 | georg.brandl | 2009-10-22 13:28:06 +0200 (Do, 22 Okt 2009) | 1 line Document new directive. ........ r75603 | georg.brandl | 2009-10-22 13:28:23 +0200 (Do, 22 Okt 2009) | 1 line Allow short form with text as argument. ........ r75604 | georg.brandl | 2009-10-22 13:36:50 +0200 (Do, 22 Okt 2009) | 1 line Fix stylesheet for multi-paragraph impl-details. ........ r75605 | georg.brandl | 2009-10-22 13:48:10 +0200 (Do, 22 Okt 2009) | 1 line Use "impl-detail" directive where applicable. ........ r75606 | georg.brandl | 2009-10-22 17:00:06 +0200 (Do, 22 Okt 2009) | 1 line #6324: membership test tries iteration via __iter__. ........ r75607 | georg.brandl | 2009-10-22 17:04:09 +0200 (Do, 22 Okt 2009) | 1 line #7088: document new functions in signal as Unix-only. ........ r75610 | georg.brandl | 2009-10-22 17:27:24 +0200 (Do, 22 Okt 2009) | 1 line Reorder __slots__ fine print and add a clarification. ........ r75611 | georg.brandl | 2009-10-22 17:42:32 +0200 (Do, 22 Okt 2009) | 1 line #7035: improve docs of the various <method>_errors() functions, and give them docstrings. ........ r75612 | georg.brandl | 2009-10-22 17:52:15 +0200 (Do, 22 Okt 2009) | 1 line #7156: document curses as Unix-only. ........ r75613 | georg.brandl | 2009-10-22 17:54:35 +0200 (Do, 22 Okt 2009) | 1 line #6977: getopt does not support optional option arguments. ........ r75616 | georg.brandl | 2009-10-22 18:17:05 +0200 (Do, 22 Okt 2009) | 1 line Add proper references. ........ r75617 | georg.brandl | 2009-10-22 18:20:55 +0200 (Do, 22 Okt 2009) | 1 line Make printout margin important. ........ r75623 | georg.brandl | 2009-10-23 10:14:44 +0200 (Fr, 23 Okt 2009) | 1 line #7188: fix optionxform() docs. ........ r75627 | fred.drake | 2009-10-23 15:04:51 +0200 (Fr, 23 Okt 2009) | 2 lines add further note about what's passed to optionxform ........ r75640 | neil.schemenauer | 2009-10-23 21:58:17 +0200 (Fr, 23 Okt 2009) | 2 lines Improve some docstrings in the 'warnings' module. ........ r75647 | georg.brandl | 2009-10-24 12:04:19 +0200 (Sa, 24 Okt 2009) | 1 line Fix markup. ........ r75696 | georg.brandl | 2009-10-25 21:25:43 +0100 (So, 25 Okt 2009) | 1 line Fix a demo. ........ r75795 | georg.brandl | 2009-10-27 16:10:22 +0100 (Di, 27 Okt 2009) | 1 line Fix a strange mis-edit. ........
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* If a class defines a slot also defined in a base class, the instance variable
defined by the base class slot is inaccessible (except by retrieving its
descriptor directly from the base class). This renders the meaning of the
program undefined. In the future, a check may be added to prevent this.
Merged revisions 66974,66977,66984,66989,66992,66994-66996,66998-67000,67007,67015 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66974 | benjamin.peterson | 2008-10-19 08:59:01 -0500 (Sun, 19 Oct 2008) | 1 line fix compiler warning ........ r66977 | benjamin.peterson | 2008-10-19 14:39:16 -0500 (Sun, 19 Oct 2008) | 1 line mention -n ........ r66984 | armin.ronacher | 2008-10-20 16:29:08 -0500 (Mon, 20 Oct 2008) | 3 lines Fixed #4062, added import for _ast.__version__ to ast to match the documented behavior. ........ r66989 | matthias.klose | 2008-10-21 04:12:25 -0500 (Tue, 21 Oct 2008) | 2 lines - install versioned manpage ........ r66992 | benjamin.peterson | 2008-10-21 15:51:13 -0500 (Tue, 21 Oct 2008) | 1 line make sure to call iteritems() ........ r66994 | amaury.forgeotdarc | 2008-10-21 17:01:38 -0500 (Tue, 21 Oct 2008) | 6 lines #4157 move two test functions out of platform.py. Turn them into unit tests, and correct an obvious typo: (("a", "b") ("c", "d") ("e", "f")) compiles even with the missing commas, but does not execute very well... ........ r66995 | benjamin.peterson | 2008-10-21 17:18:29 -0500 (Tue, 21 Oct 2008) | 1 line return ArgInfo from inspect.getargvalues #4092 ........ r66996 | benjamin.peterson | 2008-10-21 17:20:31 -0500 (Tue, 21 Oct 2008) | 1 line add NEWs note for last change ........ r66998 | benjamin.peterson | 2008-10-22 15:57:43 -0500 (Wed, 22 Oct 2008) | 1 line fix a few typos ........ r66999 | benjamin.peterson | 2008-10-22 16:05:30 -0500 (Wed, 22 Oct 2008) | 1 line and another typo... ........ r67000 | benjamin.peterson | 2008-10-22 16:16:34 -0500 (Wed, 22 Oct 2008) | 1 line fix #4150: pdb's up command didn't work for generators in post-mortem ........ r67007 | benjamin.peterson | 2008-10-23 16:43:48 -0500 (Thu, 23 Oct 2008) | 1 line only nonempty __slots__ don't work ........ r67015 | georg.brandl | 2008-10-25 02:00:52 -0500 (Sat, 25 Oct 2008) | 2 lines Typo fix. ........
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* Nonempty *__slots__* does not work for classes derived from "variable-length"
built-in types such as :class:`int`, :class:`bytes` and :class:`tuple`.
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* Any non-string iterable may be assigned to *__slots__*. Mappings may also be
used; however, in the future, special meaning may be assigned to the values
corresponding to each key.
* *__class__* assignment works only if both classes have the same *__slots__*.
* Multiple inheritance with multiple slotted parent classes can be used,
but only one parent is allowed to have attributes created by slots
(the other bases must have empty slot layouts) - violations raise
:exc:`TypeError`.
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* If an iterator is used for *__slots__* then a descriptor is created for each
of the iterator's values. However, the *__slots__* attribute will be an empty
iterator.
.. _class-customization:
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Customizing class creation
--------------------------
Whenever a class inherits from another class, *__init_subclass__* is
called on that class. This way, it is possible to write classes which
change the behavior of subclasses. This is closely related to class
decorators, but where class decorators only affect the specific class they're
applied to, ``__init_subclass__`` solely applies to future subclasses of the
class defining the method.
.. classmethod:: object.__init_subclass__(cls)
This method is called whenever the containing class is subclassed.
*cls* is then the new subclass. If defined as a normal instance method,
this method is implicitly converted to a class method.
Keyword arguments which are given to a new class are passed to
the parent's class ``__init_subclass__``. For compatibility with
other classes using ``__init_subclass__``, one should take out the
needed keyword arguments and pass the others over to the base
class, as in::
class Philosopher:
def __init_subclass__(cls, /, default_name, **kwargs):
super().__init_subclass__(**kwargs)
cls.default_name = default_name
class AustralianPhilosopher(Philosopher, default_name="Bruce"):
pass
The default implementation ``object.__init_subclass__`` does
nothing, but raises an error if it is called with any arguments.
.. note::
The metaclass hint ``metaclass`` is consumed by the rest of the type
machinery, and is never passed to ``__init_subclass__`` implementations.
The actual metaclass (rather than the explicit hint) can be accessed as
``type(cls)``.
.. versionadded:: 3.6
.. _metaclasses:
Metaclasses
^^^^^^^^^^^
.. index::
single: metaclass
builtin: type
single: = (equals); class definition
By default, classes are constructed using :func:`type`. The class body is
executed in a new namespace and the class name is bound locally to the
result of ``type(name, bases, namespace)``.
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The class creation process can be customized by passing the ``metaclass``
keyword argument in the class definition line, or by inheriting from an
existing class that included such an argument. In the following example,
both ``MyClass`` and ``MySubclass`` are instances of ``Meta``::
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class Meta(type):
pass
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class MyClass(metaclass=Meta):
pass
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class MySubclass(MyClass):
pass
Merged revisions 59822-59841 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59822 | georg.brandl | 2008-01-07 17:43:47 +0100 (Mon, 07 Jan 2008) | 2 lines Restore "somenamedtuple" as the "class" for named tuple attrs. ........ r59824 | georg.brandl | 2008-01-07 18:09:35 +0100 (Mon, 07 Jan 2008) | 2 lines Patch #602345 by Neal Norwitz and me: add -B option and PYTHONDONTWRITEBYTECODE envvar to skip writing bytecode. ........ r59827 | georg.brandl | 2008-01-07 18:25:53 +0100 (Mon, 07 Jan 2008) | 2 lines patch #1668: clarify envvar docs; rename THREADDEBUG to PYTHONTHREADDEBUG. ........ r59830 | georg.brandl | 2008-01-07 19:16:36 +0100 (Mon, 07 Jan 2008) | 2 lines Make Python compile with --disable-unicode. ........ r59831 | georg.brandl | 2008-01-07 19:23:27 +0100 (Mon, 07 Jan 2008) | 2 lines Restructure urllib doc structure. ........ r59833 | georg.brandl | 2008-01-07 19:41:34 +0100 (Mon, 07 Jan 2008) | 2 lines Fix #define ordering. ........ r59834 | georg.brandl | 2008-01-07 19:47:44 +0100 (Mon, 07 Jan 2008) | 2 lines #467924, patch by Alan McIntyre: Add ZipFile.extract and ZipFile.extractall. ........ r59835 | raymond.hettinger | 2008-01-07 19:52:19 +0100 (Mon, 07 Jan 2008) | 1 line Fix inconsistent title levels -- it made the whole doc build crash horribly. ........ r59836 | georg.brandl | 2008-01-07 19:57:03 +0100 (Mon, 07 Jan 2008) | 2 lines Fix two further doc build warnings. ........ r59837 | georg.brandl | 2008-01-07 20:17:10 +0100 (Mon, 07 Jan 2008) | 2 lines Clarify metaclass docs and add example. ........ r59838 | vinay.sajip | 2008-01-07 20:40:10 +0100 (Mon, 07 Jan 2008) | 1 line Added section about adding contextual information to log output. ........ r59839 | christian.heimes | 2008-01-07 20:58:41 +0100 (Mon, 07 Jan 2008) | 1 line Fixed indention problem that caused the second TIPC test to run on systems without TIPC ........ r59840 | raymond.hettinger | 2008-01-07 21:07:38 +0100 (Mon, 07 Jan 2008) | 1 line Cleanup named tuple subclassing example. ........
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Any other keyword arguments that are specified in the class definition are
passed through to all metaclass operations described below.
Merged revisions 59822-59841 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59822 | georg.brandl | 2008-01-07 17:43:47 +0100 (Mon, 07 Jan 2008) | 2 lines Restore "somenamedtuple" as the "class" for named tuple attrs. ........ r59824 | georg.brandl | 2008-01-07 18:09:35 +0100 (Mon, 07 Jan 2008) | 2 lines Patch #602345 by Neal Norwitz and me: add -B option and PYTHONDONTWRITEBYTECODE envvar to skip writing bytecode. ........ r59827 | georg.brandl | 2008-01-07 18:25:53 +0100 (Mon, 07 Jan 2008) | 2 lines patch #1668: clarify envvar docs; rename THREADDEBUG to PYTHONTHREADDEBUG. ........ r59830 | georg.brandl | 2008-01-07 19:16:36 +0100 (Mon, 07 Jan 2008) | 2 lines Make Python compile with --disable-unicode. ........ r59831 | georg.brandl | 2008-01-07 19:23:27 +0100 (Mon, 07 Jan 2008) | 2 lines Restructure urllib doc structure. ........ r59833 | georg.brandl | 2008-01-07 19:41:34 +0100 (Mon, 07 Jan 2008) | 2 lines Fix #define ordering. ........ r59834 | georg.brandl | 2008-01-07 19:47:44 +0100 (Mon, 07 Jan 2008) | 2 lines #467924, patch by Alan McIntyre: Add ZipFile.extract and ZipFile.extractall. ........ r59835 | raymond.hettinger | 2008-01-07 19:52:19 +0100 (Mon, 07 Jan 2008) | 1 line Fix inconsistent title levels -- it made the whole doc build crash horribly. ........ r59836 | georg.brandl | 2008-01-07 19:57:03 +0100 (Mon, 07 Jan 2008) | 2 lines Fix two further doc build warnings. ........ r59837 | georg.brandl | 2008-01-07 20:17:10 +0100 (Mon, 07 Jan 2008) | 2 lines Clarify metaclass docs and add example. ........ r59838 | vinay.sajip | 2008-01-07 20:40:10 +0100 (Mon, 07 Jan 2008) | 1 line Added section about adding contextual information to log output. ........ r59839 | christian.heimes | 2008-01-07 20:58:41 +0100 (Mon, 07 Jan 2008) | 1 line Fixed indention problem that caused the second TIPC test to run on systems without TIPC ........ r59840 | raymond.hettinger | 2008-01-07 21:07:38 +0100 (Mon, 07 Jan 2008) | 1 line Cleanup named tuple subclassing example. ........
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When a class definition is executed, the following steps occur:
Merged revisions 59822-59841 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59822 | georg.brandl | 2008-01-07 17:43:47 +0100 (Mon, 07 Jan 2008) | 2 lines Restore "somenamedtuple" as the "class" for named tuple attrs. ........ r59824 | georg.brandl | 2008-01-07 18:09:35 +0100 (Mon, 07 Jan 2008) | 2 lines Patch #602345 by Neal Norwitz and me: add -B option and PYTHONDONTWRITEBYTECODE envvar to skip writing bytecode. ........ r59827 | georg.brandl | 2008-01-07 18:25:53 +0100 (Mon, 07 Jan 2008) | 2 lines patch #1668: clarify envvar docs; rename THREADDEBUG to PYTHONTHREADDEBUG. ........ r59830 | georg.brandl | 2008-01-07 19:16:36 +0100 (Mon, 07 Jan 2008) | 2 lines Make Python compile with --disable-unicode. ........ r59831 | georg.brandl | 2008-01-07 19:23:27 +0100 (Mon, 07 Jan 2008) | 2 lines Restructure urllib doc structure. ........ r59833 | georg.brandl | 2008-01-07 19:41:34 +0100 (Mon, 07 Jan 2008) | 2 lines Fix #define ordering. ........ r59834 | georg.brandl | 2008-01-07 19:47:44 +0100 (Mon, 07 Jan 2008) | 2 lines #467924, patch by Alan McIntyre: Add ZipFile.extract and ZipFile.extractall. ........ r59835 | raymond.hettinger | 2008-01-07 19:52:19 +0100 (Mon, 07 Jan 2008) | 1 line Fix inconsistent title levels -- it made the whole doc build crash horribly. ........ r59836 | georg.brandl | 2008-01-07 19:57:03 +0100 (Mon, 07 Jan 2008) | 2 lines Fix two further doc build warnings. ........ r59837 | georg.brandl | 2008-01-07 20:17:10 +0100 (Mon, 07 Jan 2008) | 2 lines Clarify metaclass docs and add example. ........ r59838 | vinay.sajip | 2008-01-07 20:40:10 +0100 (Mon, 07 Jan 2008) | 1 line Added section about adding contextual information to log output. ........ r59839 | christian.heimes | 2008-01-07 20:58:41 +0100 (Mon, 07 Jan 2008) | 1 line Fixed indention problem that caused the second TIPC test to run on systems without TIPC ........ r59840 | raymond.hettinger | 2008-01-07 21:07:38 +0100 (Mon, 07 Jan 2008) | 1 line Cleanup named tuple subclassing example. ........
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* MRO entries are resolved;
* the appropriate metaclass is determined;
* the class namespace is prepared;
* the class body is executed;
* the class object is created.
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Resolving MRO entries
^^^^^^^^^^^^^^^^^^^^^
If a base that appears in class definition is not an instance of :class:`type`,
then an ``__mro_entries__`` method is searched on it. If found, it is called
with the original bases tuple. This method must return a tuple of classes that
will be used instead of this base. The tuple may be empty, in such case
the original base is ignored.
.. seealso::
:pep:`560` - Core support for typing module and generic types
Determining the appropriate metaclass
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. index::
single: metaclass hint
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The appropriate metaclass for a class definition is determined as follows:
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* if no bases and no explicit metaclass are given, then :func:`type` is used;
* if an explicit metaclass is given and it is *not* an instance of
:func:`type`, then it is used directly as the metaclass;
* if an instance of :func:`type` is given as the explicit metaclass, or
bases are defined, then the most derived metaclass is used.
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The most derived metaclass is selected from the explicitly specified
metaclass (if any) and the metaclasses (i.e. ``type(cls)``) of all specified
base classes. The most derived metaclass is one which is a subtype of *all*
of these candidate metaclasses. If none of the candidate metaclasses meets
that criterion, then the class definition will fail with ``TypeError``.
.. _prepare:
Preparing the class namespace
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. index::
single: __prepare__ (metaclass method)
Once the appropriate metaclass has been identified, then the class namespace
is prepared. If the metaclass has a ``__prepare__`` attribute, it is called
as ``namespace = metaclass.__prepare__(name, bases, **kwds)`` (where the
additional keyword arguments, if any, come from the class definition). The
``__prepare__`` method should be implemented as a :func:`classmethod`. The
namespace returned by ``__prepare__`` is passed in to ``__new__``, but when
the final class object is created the namespace is copied into a new ``dict``.
If the metaclass has no ``__prepare__`` attribute, then the class namespace
is initialised as an empty ordered mapping.
.. seealso::
:pep:`3115` - Metaclasses in Python 3000
Introduced the ``__prepare__`` namespace hook
Executing the class body
^^^^^^^^^^^^^^^^^^^^^^^^
.. index::
single: class; body
The class body is executed (approximately) as
``exec(body, globals(), namespace)``. The key difference from a normal
call to :func:`exec` is that lexical scoping allows the class body (including
any methods) to reference names from the current and outer scopes when the
class definition occurs inside a function.
However, even when the class definition occurs inside the function, methods
defined inside the class still cannot see names defined at the class scope.
Class variables must be accessed through the first parameter of instance or
class methods, or through the implicit lexically scoped ``__class__`` reference
described in the next section.
.. _class-object-creation:
Creating the class object
^^^^^^^^^^^^^^^^^^^^^^^^^
.. index::
single: __class__ (method cell)
single: __classcell__ (class namespace entry)
Once the class namespace has been populated by executing the class body,
the class object is created by calling
``metaclass(name, bases, namespace, **kwds)`` (the additional keywords
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passed here are the same as those passed to ``__prepare__``).
This class object is the one that will be referenced by the zero-argument
form of :func:`super`. ``__class__`` is an implicit closure reference
created by the compiler if any methods in a class body refer to either
``__class__`` or ``super``. This allows the zero argument form of
:func:`super` to correctly identify the class being defined based on
lexical scoping, while the class or instance that was used to make the
current call is identified based on the first argument passed to the method.
.. impl-detail::
In CPython 3.6 and later, the ``__class__`` cell is passed to the metaclass
as a ``__classcell__`` entry in the class namespace. If present, this must
be propagated up to the ``type.__new__`` call in order for the class to be
initialised correctly.
Failing to do so will result in a :exc:`RuntimeError` in Python 3.8.
When using the default metaclass :class:`type`, or any metaclass that ultimately
calls ``type.__new__``, the following additional customisation steps are
invoked after creating the class object:
* first, ``type.__new__`` collects all of the descriptors in the class
namespace that define a :meth:`~object.__set_name__` method;
* second, all of these ``__set_name__`` methods are called with the class
being defined and the assigned name of that particular descriptor;
* finally, the :meth:`~object.__init_subclass__` hook is called on the
immediate parent of the new class in its method resolution order.
After the class object is created, it is passed to the class decorators
included in the class definition (if any) and the resulting object is bound
in the local namespace as the defined class.
When a new class is created by ``type.__new__``, the object provided as the
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namespace parameter is copied to a new ordered mapping and the original
object is discarded. The new copy is wrapped in a read-only proxy, which
becomes the :attr:`~object.__dict__` attribute of the class object.
.. seealso::
:pep:`3135` - New super
Describes the implicit ``__class__`` closure reference
Uses for metaclasses
^^^^^^^^^^^^^^^^^^^^
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The potential uses for metaclasses are boundless. Some ideas that have been
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explored include enum, logging, interface checking, automatic delegation,
automatic property creation, proxies, frameworks, and automatic resource
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locking/synchronization.
Merged revisions 80030,80067,80069,80080-80081,80084,80432-80433,80465-80470,81059,81065-81067 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r80030 | georg.brandl | 2010-04-13 08:43:54 +0200 (Di, 13 Apr 2010) | 1 line Get rid of multi-row cells. ........ r80067 | georg.brandl | 2010-04-14 10:53:38 +0200 (Mi, 14 Apr 2010) | 1 line #5341: typo. ........ r80069 | georg.brandl | 2010-04-14 15:50:31 +0200 (Mi, 14 Apr 2010) | 1 line Add an x-ref to where the O_ constants are documented and move the SEEK_ constants after lseek(). ........ r80080 | georg.brandl | 2010-04-14 21:16:38 +0200 (Mi, 14 Apr 2010) | 1 line #8399: add note about Windows and O_BINARY. ........ r80081 | georg.brandl | 2010-04-14 23:34:44 +0200 (Mi, 14 Apr 2010) | 1 line #5250: document __instancecheck__ and __subclasscheck__. I hope the part about the class/metaclass distinction is understandable. ........ r80084 | georg.brandl | 2010-04-14 23:46:45 +0200 (Mi, 14 Apr 2010) | 1 line Fix missing. ........ r80432 | georg.brandl | 2010-04-24 10:56:58 +0200 (Sa, 24 Apr 2010) | 1 line Markup fixes. ........ r80433 | georg.brandl | 2010-04-24 11:08:10 +0200 (Sa, 24 Apr 2010) | 1 line #7507: quote "!" in pipes.quote(); it is a special character for some shells. ........ r80465 | georg.brandl | 2010-04-25 12:29:17 +0200 (So, 25 Apr 2010) | 1 line Remove LaTeXy index entry syntax. ........ r80466 | georg.brandl | 2010-04-25 12:54:42 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Better cross-referencing in socket and winreg docs. ........ r80467 | georg.brandl | 2010-04-25 12:55:16 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Remove reference to winreg being the fabled high-level registry interface. ........ r80468 | georg.brandl | 2010-04-25 12:55:58 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Minor spelling changes to _winreg docs. ........ r80469 | georg.brandl | 2010-04-25 12:56:41 +0200 (So, 25 Apr 2010) | 1 line Fix code example to have valid syntax so that it can be highlighted. ........ r80470 | georg.brandl | 2010-04-25 12:57:15 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Make socket setblocking <-> settimeout examples symmetric. ........ r81059 | georg.brandl | 2010-05-10 23:02:51 +0200 (Mo, 10 Mai 2010) | 1 line #8642: fix wrong function name. ........ r81065 | georg.brandl | 2010-05-10 23:46:50 +0200 (Mo, 10 Mai 2010) | 1 line Fix reference direction. ........ r81066 | georg.brandl | 2010-05-10 23:50:57 +0200 (Mo, 10 Mai 2010) | 1 line Consolidate deprecation messages. ........ r81067 | georg.brandl | 2010-05-10 23:51:33 +0200 (Mo, 10 Mai 2010) | 1 line Fix typo. ........
2010-05-19 17:57:08 -03:00
Customizing instance and subclass checks
----------------------------------------
The following methods are used to override the default behavior of the
:func:`isinstance` and :func:`issubclass` built-in functions.
In particular, the metaclass :class:`abc.ABCMeta` implements these methods in
order to allow the addition of Abstract Base Classes (ABCs) as "virtual base
Merged revisions 80605-80609,80642-80646,80651-80652,80674,80684-80686,80748,80852,80854,80870,80872-80873,80907,80915-80916,80951-80952,80976-80977,80985,81038-81040,81042,81053,81070,81104-81105,81114,81125,81245,81285,81402,81463,81516,81562-81563,81567,81593,81635,81680-81681,81684,81801,81888,81931-81933,81939-81942,81963,81984,81991,82120,82188,82264-82267 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r80605 | andrew.kuchling | 2010-04-28 19:22:16 -0500 (Wed, 28 Apr 2010) | 1 line Add various items ........ r80606 | andrew.kuchling | 2010-04-28 20:44:30 -0500 (Wed, 28 Apr 2010) | 6 lines Fix doubled 'the'. Markup fixes to use :exc:, :option: in a few places. (Glitch: unittest.main's -c ends up a link to the Python interpreter's -c option. Should we skip using :option: for that switch, or disable the auto-linking somehow?) ........ r80607 | andrew.kuchling | 2010-04-28 20:45:41 -0500 (Wed, 28 Apr 2010) | 1 line Add various unittest items ........ r80608 | benjamin.peterson | 2010-04-28 22:18:05 -0500 (Wed, 28 Apr 2010) | 1 line update pypy description ........ r80609 | benjamin.peterson | 2010-04-28 22:30:59 -0500 (Wed, 28 Apr 2010) | 1 line update pypy url ........ r80642 | andrew.kuchling | 2010-04-29 19:49:09 -0500 (Thu, 29 Apr 2010) | 1 line Always add space after RFC; reword paragraph ........ r80643 | andrew.kuchling | 2010-04-29 19:52:31 -0500 (Thu, 29 Apr 2010) | 6 lines Reword paragraph to make its meaning clearer. Antoine Pitrou: is my version of the paragraph still correct? R. David Murray: is this more understandable than the previous version? ........ r80644 | andrew.kuchling | 2010-04-29 20:02:15 -0500 (Thu, 29 Apr 2010) | 1 line Fix typos ........ r80645 | andrew.kuchling | 2010-04-29 20:32:47 -0500 (Thu, 29 Apr 2010) | 1 line Markup fix; clarify by adding 'in that order' ........ r80646 | andrew.kuchling | 2010-04-29 20:33:40 -0500 (Thu, 29 Apr 2010) | 1 line Add various items; rearrange unittest section a bit ........ r80651 | andrew.kuchling | 2010-04-30 08:46:55 -0500 (Fri, 30 Apr 2010) | 1 line Minor grammar re-wording ........ r80652 | andrew.kuchling | 2010-04-30 08:47:34 -0500 (Fri, 30 Apr 2010) | 1 line Add item ........ r80674 | andrew.kuchling | 2010-04-30 20:19:16 -0500 (Fri, 30 Apr 2010) | 1 line Add various items ........ r80684 | andrew.kuchling | 2010-05-01 07:05:52 -0500 (Sat, 01 May 2010) | 1 line Minor grammar fix ........ r80685 | andrew.kuchling | 2010-05-01 07:06:51 -0500 (Sat, 01 May 2010) | 1 line Describe memoryview ........ r80686 | antoine.pitrou | 2010-05-01 07:16:39 -0500 (Sat, 01 May 2010) | 4 lines Fix attribution. Travis didn't do much and he did a bad work. (yes, this is a sensitive subject, sorry) ........ r80748 | andrew.kuchling | 2010-05-03 20:24:22 -0500 (Mon, 03 May 2010) | 1 line Add some more items; the urlparse change is added twice ........ r80852 | andrew.kuchling | 2010-05-05 20:09:47 -0500 (Wed, 05 May 2010) | 1 line Reword paragraph; fix filename, which should be pyconfig.h ........ r80854 | andrew.kuchling | 2010-05-05 20:10:56 -0500 (Wed, 05 May 2010) | 1 line Add various items ........ r80870 | andrew.kuchling | 2010-05-06 09:14:09 -0500 (Thu, 06 May 2010) | 1 line Describe ElementTree 1.3; rearrange new-module sections; describe dict views as sets; small edits and items ........ r80872 | andrew.kuchling | 2010-05-06 12:21:59 -0500 (Thu, 06 May 2010) | 1 line Add 2 items; record ideas for two initial sections; clarify wording ........ r80873 | andrew.kuchling | 2010-05-06 12:27:57 -0500 (Thu, 06 May 2010) | 1 line Change section title; point to unittest2 ........ r80907 | andrew.kuchling | 2010-05-06 20:45:14 -0500 (Thu, 06 May 2010) | 1 line Add a new section on the development plan; add an item ........ r80915 | antoine.pitrou | 2010-05-07 05:15:51 -0500 (Fri, 07 May 2010) | 3 lines Fix some markup and a class name. Also, wrap a long line. ........ r80916 | andrew.kuchling | 2010-05-07 06:30:47 -0500 (Fri, 07 May 2010) | 1 line Re-word text ........ r80951 | andrew.kuchling | 2010-05-07 20:15:26 -0500 (Fri, 07 May 2010) | 1 line Add two items ........ r80952 | andrew.kuchling | 2010-05-07 20:35:55 -0500 (Fri, 07 May 2010) | 1 line Get accents correct ........ r80976 | andrew.kuchling | 2010-05-08 08:28:03 -0500 (Sat, 08 May 2010) | 1 line Add logging.dictConfig example; give up on writing a Ttk example ........ r80977 | andrew.kuchling | 2010-05-08 08:29:46 -0500 (Sat, 08 May 2010) | 1 line Markup fixes ........ r80985 | andrew.kuchling | 2010-05-08 10:39:46 -0500 (Sat, 08 May 2010) | 7 lines Write summary of the 2.7 release; rewrite the future section some more; mention PYTHONWARNINGS env. var; tweak some examples for readability. And with this commit, the "What's New" is done... except for a complete read-through to polish the text, and fixing any reported errors, but those tasks can easily wait until after beta2. ........ r81038 | benjamin.peterson | 2010-05-09 16:09:40 -0500 (Sun, 09 May 2010) | 1 line finish clause ........ r81039 | andrew.kuchling | 2010-05-10 09:18:27 -0500 (Mon, 10 May 2010) | 1 line Markup fix; re-word a sentence ........ r81040 | andrew.kuchling | 2010-05-10 09:20:12 -0500 (Mon, 10 May 2010) | 1 line Use title case ........ r81042 | andrew.kuchling | 2010-05-10 10:03:35 -0500 (Mon, 10 May 2010) | 1 line Link to unittest2 article ........ r81053 | florent.xicluna | 2010-05-10 14:59:22 -0500 (Mon, 10 May 2010) | 2 lines Add a link on maketrans(). ........ r81070 | andrew.kuchling | 2010-05-10 18:13:41 -0500 (Mon, 10 May 2010) | 1 line Fix typo ........ r81104 | andrew.kuchling | 2010-05-11 19:38:44 -0500 (Tue, 11 May 2010) | 1 line Revision pass: lots of edits, typo fixes, rearrangements ........ r81105 | andrew.kuchling | 2010-05-11 19:40:47 -0500 (Tue, 11 May 2010) | 1 line Let's call this done ........ r81114 | andrew.kuchling | 2010-05-12 08:56:07 -0500 (Wed, 12 May 2010) | 1 line Grammar fix ........ r81125 | andrew.kuchling | 2010-05-12 13:56:48 -0500 (Wed, 12 May 2010) | 1 line #8696: add documentation for logging.config.dictConfig (PEP 391) ........ r81245 | andrew.kuchling | 2010-05-16 18:31:16 -0500 (Sun, 16 May 2010) | 1 line Add cross-reference to later section ........ r81285 | vinay.sajip | 2010-05-18 03:16:27 -0500 (Tue, 18 May 2010) | 1 line Fixed minor typo in ReST markup. ........ r81402 | vinay.sajip | 2010-05-21 12:41:34 -0500 (Fri, 21 May 2010) | 1 line Updated logging documentation with more dictConfig information. ........ r81463 | georg.brandl | 2010-05-22 03:17:23 -0500 (Sat, 22 May 2010) | 1 line #8785: less confusing description of regex.find*. ........ r81516 | andrew.kuchling | 2010-05-25 08:34:08 -0500 (Tue, 25 May 2010) | 1 line Add three items ........ r81562 | andrew.kuchling | 2010-05-27 08:22:53 -0500 (Thu, 27 May 2010) | 1 line Rewrite wxWidgets section ........ r81563 | andrew.kuchling | 2010-05-27 08:30:09 -0500 (Thu, 27 May 2010) | 1 line Remove top-level 'General Questions' section, pushing up the questions it contains ........ r81567 | andrew.kuchling | 2010-05-27 16:29:59 -0500 (Thu, 27 May 2010) | 1 line Add item ........ r81593 | georg.brandl | 2010-05-29 03:46:18 -0500 (Sat, 29 May 2010) | 1 line #8616: add new turtle demo "nim". ........ r81635 | georg.brandl | 2010-06-01 02:25:23 -0500 (Tue, 01 Jun 2010) | 1 line Put docs for RegexObject.search() before RegexObject.match() to mirror re.search() and re.match() order. ........ r81680 | vinay.sajip | 2010-06-03 17:34:42 -0500 (Thu, 03 Jun 2010) | 1 line Issue #8890: Documentation changed to avoid reference to temporary files. ........ r81681 | sean.reifschneider | 2010-06-03 20:51:26 -0500 (Thu, 03 Jun 2010) | 2 lines Issue8810: Clearing up docstring for tzinfo.utcoffset. ........ r81684 | vinay.sajip | 2010-06-04 08:41:02 -0500 (Fri, 04 Jun 2010) | 1 line Issue #8890: Documentation changed to avoid reference to temporary files - other cases covered. ........ r81801 | andrew.kuchling | 2010-06-07 08:38:40 -0500 (Mon, 07 Jun 2010) | 1 line #8875: Remove duplicated paragraph ........ r81888 | andrew.kuchling | 2010-06-10 20:54:58 -0500 (Thu, 10 Jun 2010) | 1 line Add a few more items ........ r81931 | georg.brandl | 2010-06-12 01:26:54 -0500 (Sat, 12 Jun 2010) | 1 line Fix punctuation. ........ r81932 | georg.brandl | 2010-06-12 01:28:58 -0500 (Sat, 12 Jun 2010) | 1 line Document that an existing directory raises in mkdir(). ........ r81933 | georg.brandl | 2010-06-12 01:45:33 -0500 (Sat, 12 Jun 2010) | 1 line Update version in README. ........ r81939 | georg.brandl | 2010-06-12 04:45:01 -0500 (Sat, 12 Jun 2010) | 1 line Use newer toctree syntax. ........ r81940 | georg.brandl | 2010-06-12 04:45:28 -0500 (Sat, 12 Jun 2010) | 1 line Add document on how to build. ........ r81941 | georg.brandl | 2010-06-12 04:45:58 -0500 (Sat, 12 Jun 2010) | 1 line Fix gratuitous indentation. ........ r81942 | georg.brandl | 2010-06-12 04:46:03 -0500 (Sat, 12 Jun 2010) | 1 line Update README. ........ r81963 | andrew.kuchling | 2010-06-12 15:00:55 -0500 (Sat, 12 Jun 2010) | 1 line Grammar fix ........ r81984 | georg.brandl | 2010-06-14 10:58:39 -0500 (Mon, 14 Jun 2010) | 1 line #8993: fix reference. ........ r81991 | andrew.kuchling | 2010-06-14 19:38:58 -0500 (Mon, 14 Jun 2010) | 1 line Add another bunch of items ........ r82120 | andrew.kuchling | 2010-06-20 16:45:45 -0500 (Sun, 20 Jun 2010) | 1 line Note that Python 3.x isn't covered; add forward ref. for UTF-8; note error in 2.5 and up ........ r82188 | benjamin.peterson | 2010-06-23 19:02:46 -0500 (Wed, 23 Jun 2010) | 1 line remove reverted changed ........ r82264 | georg.brandl | 2010-06-27 05:47:47 -0500 (Sun, 27 Jun 2010) | 1 line Confusing punctuation. ........ r82265 | georg.brandl | 2010-06-27 05:49:23 -0500 (Sun, 27 Jun 2010) | 1 line Use designated syntax for optional grammar element. ........ r82266 | georg.brandl | 2010-06-27 05:51:44 -0500 (Sun, 27 Jun 2010) | 1 line Fix URL. ........ r82267 | georg.brandl | 2010-06-27 05:55:38 -0500 (Sun, 27 Jun 2010) | 1 line Two typos. ........
2010-06-27 19:32:30 -03:00
classes" to any class or type (including built-in types), including other
Merged revisions 80030,80067,80069,80080-80081,80084,80432-80433,80465-80470,81059,81065-81067 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r80030 | georg.brandl | 2010-04-13 08:43:54 +0200 (Di, 13 Apr 2010) | 1 line Get rid of multi-row cells. ........ r80067 | georg.brandl | 2010-04-14 10:53:38 +0200 (Mi, 14 Apr 2010) | 1 line #5341: typo. ........ r80069 | georg.brandl | 2010-04-14 15:50:31 +0200 (Mi, 14 Apr 2010) | 1 line Add an x-ref to where the O_ constants are documented and move the SEEK_ constants after lseek(). ........ r80080 | georg.brandl | 2010-04-14 21:16:38 +0200 (Mi, 14 Apr 2010) | 1 line #8399: add note about Windows and O_BINARY. ........ r80081 | georg.brandl | 2010-04-14 23:34:44 +0200 (Mi, 14 Apr 2010) | 1 line #5250: document __instancecheck__ and __subclasscheck__. I hope the part about the class/metaclass distinction is understandable. ........ r80084 | georg.brandl | 2010-04-14 23:46:45 +0200 (Mi, 14 Apr 2010) | 1 line Fix missing. ........ r80432 | georg.brandl | 2010-04-24 10:56:58 +0200 (Sa, 24 Apr 2010) | 1 line Markup fixes. ........ r80433 | georg.brandl | 2010-04-24 11:08:10 +0200 (Sa, 24 Apr 2010) | 1 line #7507: quote "!" in pipes.quote(); it is a special character for some shells. ........ r80465 | georg.brandl | 2010-04-25 12:29:17 +0200 (So, 25 Apr 2010) | 1 line Remove LaTeXy index entry syntax. ........ r80466 | georg.brandl | 2010-04-25 12:54:42 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Better cross-referencing in socket and winreg docs. ........ r80467 | georg.brandl | 2010-04-25 12:55:16 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Remove reference to winreg being the fabled high-level registry interface. ........ r80468 | georg.brandl | 2010-04-25 12:55:58 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Minor spelling changes to _winreg docs. ........ r80469 | georg.brandl | 2010-04-25 12:56:41 +0200 (So, 25 Apr 2010) | 1 line Fix code example to have valid syntax so that it can be highlighted. ........ r80470 | georg.brandl | 2010-04-25 12:57:15 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Make socket setblocking <-> settimeout examples symmetric. ........ r81059 | georg.brandl | 2010-05-10 23:02:51 +0200 (Mo, 10 Mai 2010) | 1 line #8642: fix wrong function name. ........ r81065 | georg.brandl | 2010-05-10 23:46:50 +0200 (Mo, 10 Mai 2010) | 1 line Fix reference direction. ........ r81066 | georg.brandl | 2010-05-10 23:50:57 +0200 (Mo, 10 Mai 2010) | 1 line Consolidate deprecation messages. ........ r81067 | georg.brandl | 2010-05-10 23:51:33 +0200 (Mo, 10 Mai 2010) | 1 line Fix typo. ........
2010-05-19 17:57:08 -03:00
ABCs.
.. method:: class.__instancecheck__(self, instance)
Return true if *instance* should be considered a (direct or indirect)
instance of *class*. If defined, called to implement ``isinstance(instance,
class)``.
.. method:: class.__subclasscheck__(self, subclass)
Return true if *subclass* should be considered a (direct or indirect)
subclass of *class*. If defined, called to implement ``issubclass(subclass,
class)``.
Note that these methods are looked up on the type (metaclass) of a class. They
cannot be defined as class methods in the actual class. This is consistent with
Merged revisions 80605-80609,80642-80646,80651-80652,80674,80684-80686,80748,80852,80854,80870,80872-80873,80907,80915-80916,80951-80952,80976-80977,80985,81038-81040,81042,81053,81070,81104-81105,81114,81125,81245,81285,81402,81463,81516,81562-81563,81567,81593,81635,81680-81681,81684,81801,81888,81931-81933,81939-81942,81963,81984,81991,82120,82188,82264-82267 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r80605 | andrew.kuchling | 2010-04-28 19:22:16 -0500 (Wed, 28 Apr 2010) | 1 line Add various items ........ r80606 | andrew.kuchling | 2010-04-28 20:44:30 -0500 (Wed, 28 Apr 2010) | 6 lines Fix doubled 'the'. Markup fixes to use :exc:, :option: in a few places. (Glitch: unittest.main's -c ends up a link to the Python interpreter's -c option. Should we skip using :option: for that switch, or disable the auto-linking somehow?) ........ r80607 | andrew.kuchling | 2010-04-28 20:45:41 -0500 (Wed, 28 Apr 2010) | 1 line Add various unittest items ........ r80608 | benjamin.peterson | 2010-04-28 22:18:05 -0500 (Wed, 28 Apr 2010) | 1 line update pypy description ........ r80609 | benjamin.peterson | 2010-04-28 22:30:59 -0500 (Wed, 28 Apr 2010) | 1 line update pypy url ........ r80642 | andrew.kuchling | 2010-04-29 19:49:09 -0500 (Thu, 29 Apr 2010) | 1 line Always add space after RFC; reword paragraph ........ r80643 | andrew.kuchling | 2010-04-29 19:52:31 -0500 (Thu, 29 Apr 2010) | 6 lines Reword paragraph to make its meaning clearer. Antoine Pitrou: is my version of the paragraph still correct? R. David Murray: is this more understandable than the previous version? ........ r80644 | andrew.kuchling | 2010-04-29 20:02:15 -0500 (Thu, 29 Apr 2010) | 1 line Fix typos ........ r80645 | andrew.kuchling | 2010-04-29 20:32:47 -0500 (Thu, 29 Apr 2010) | 1 line Markup fix; clarify by adding 'in that order' ........ r80646 | andrew.kuchling | 2010-04-29 20:33:40 -0500 (Thu, 29 Apr 2010) | 1 line Add various items; rearrange unittest section a bit ........ r80651 | andrew.kuchling | 2010-04-30 08:46:55 -0500 (Fri, 30 Apr 2010) | 1 line Minor grammar re-wording ........ r80652 | andrew.kuchling | 2010-04-30 08:47:34 -0500 (Fri, 30 Apr 2010) | 1 line Add item ........ r80674 | andrew.kuchling | 2010-04-30 20:19:16 -0500 (Fri, 30 Apr 2010) | 1 line Add various items ........ r80684 | andrew.kuchling | 2010-05-01 07:05:52 -0500 (Sat, 01 May 2010) | 1 line Minor grammar fix ........ r80685 | andrew.kuchling | 2010-05-01 07:06:51 -0500 (Sat, 01 May 2010) | 1 line Describe memoryview ........ r80686 | antoine.pitrou | 2010-05-01 07:16:39 -0500 (Sat, 01 May 2010) | 4 lines Fix attribution. Travis didn't do much and he did a bad work. (yes, this is a sensitive subject, sorry) ........ r80748 | andrew.kuchling | 2010-05-03 20:24:22 -0500 (Mon, 03 May 2010) | 1 line Add some more items; the urlparse change is added twice ........ r80852 | andrew.kuchling | 2010-05-05 20:09:47 -0500 (Wed, 05 May 2010) | 1 line Reword paragraph; fix filename, which should be pyconfig.h ........ r80854 | andrew.kuchling | 2010-05-05 20:10:56 -0500 (Wed, 05 May 2010) | 1 line Add various items ........ r80870 | andrew.kuchling | 2010-05-06 09:14:09 -0500 (Thu, 06 May 2010) | 1 line Describe ElementTree 1.3; rearrange new-module sections; describe dict views as sets; small edits and items ........ r80872 | andrew.kuchling | 2010-05-06 12:21:59 -0500 (Thu, 06 May 2010) | 1 line Add 2 items; record ideas for two initial sections; clarify wording ........ r80873 | andrew.kuchling | 2010-05-06 12:27:57 -0500 (Thu, 06 May 2010) | 1 line Change section title; point to unittest2 ........ r80907 | andrew.kuchling | 2010-05-06 20:45:14 -0500 (Thu, 06 May 2010) | 1 line Add a new section on the development plan; add an item ........ r80915 | antoine.pitrou | 2010-05-07 05:15:51 -0500 (Fri, 07 May 2010) | 3 lines Fix some markup and a class name. Also, wrap a long line. ........ r80916 | andrew.kuchling | 2010-05-07 06:30:47 -0500 (Fri, 07 May 2010) | 1 line Re-word text ........ r80951 | andrew.kuchling | 2010-05-07 20:15:26 -0500 (Fri, 07 May 2010) | 1 line Add two items ........ r80952 | andrew.kuchling | 2010-05-07 20:35:55 -0500 (Fri, 07 May 2010) | 1 line Get accents correct ........ r80976 | andrew.kuchling | 2010-05-08 08:28:03 -0500 (Sat, 08 May 2010) | 1 line Add logging.dictConfig example; give up on writing a Ttk example ........ r80977 | andrew.kuchling | 2010-05-08 08:29:46 -0500 (Sat, 08 May 2010) | 1 line Markup fixes ........ r80985 | andrew.kuchling | 2010-05-08 10:39:46 -0500 (Sat, 08 May 2010) | 7 lines Write summary of the 2.7 release; rewrite the future section some more; mention PYTHONWARNINGS env. var; tweak some examples for readability. And with this commit, the "What's New" is done... except for a complete read-through to polish the text, and fixing any reported errors, but those tasks can easily wait until after beta2. ........ r81038 | benjamin.peterson | 2010-05-09 16:09:40 -0500 (Sun, 09 May 2010) | 1 line finish clause ........ r81039 | andrew.kuchling | 2010-05-10 09:18:27 -0500 (Mon, 10 May 2010) | 1 line Markup fix; re-word a sentence ........ r81040 | andrew.kuchling | 2010-05-10 09:20:12 -0500 (Mon, 10 May 2010) | 1 line Use title case ........ r81042 | andrew.kuchling | 2010-05-10 10:03:35 -0500 (Mon, 10 May 2010) | 1 line Link to unittest2 article ........ r81053 | florent.xicluna | 2010-05-10 14:59:22 -0500 (Mon, 10 May 2010) | 2 lines Add a link on maketrans(). ........ r81070 | andrew.kuchling | 2010-05-10 18:13:41 -0500 (Mon, 10 May 2010) | 1 line Fix typo ........ r81104 | andrew.kuchling | 2010-05-11 19:38:44 -0500 (Tue, 11 May 2010) | 1 line Revision pass: lots of edits, typo fixes, rearrangements ........ r81105 | andrew.kuchling | 2010-05-11 19:40:47 -0500 (Tue, 11 May 2010) | 1 line Let's call this done ........ r81114 | andrew.kuchling | 2010-05-12 08:56:07 -0500 (Wed, 12 May 2010) | 1 line Grammar fix ........ r81125 | andrew.kuchling | 2010-05-12 13:56:48 -0500 (Wed, 12 May 2010) | 1 line #8696: add documentation for logging.config.dictConfig (PEP 391) ........ r81245 | andrew.kuchling | 2010-05-16 18:31:16 -0500 (Sun, 16 May 2010) | 1 line Add cross-reference to later section ........ r81285 | vinay.sajip | 2010-05-18 03:16:27 -0500 (Tue, 18 May 2010) | 1 line Fixed minor typo in ReST markup. ........ r81402 | vinay.sajip | 2010-05-21 12:41:34 -0500 (Fri, 21 May 2010) | 1 line Updated logging documentation with more dictConfig information. ........ r81463 | georg.brandl | 2010-05-22 03:17:23 -0500 (Sat, 22 May 2010) | 1 line #8785: less confusing description of regex.find*. ........ r81516 | andrew.kuchling | 2010-05-25 08:34:08 -0500 (Tue, 25 May 2010) | 1 line Add three items ........ r81562 | andrew.kuchling | 2010-05-27 08:22:53 -0500 (Thu, 27 May 2010) | 1 line Rewrite wxWidgets section ........ r81563 | andrew.kuchling | 2010-05-27 08:30:09 -0500 (Thu, 27 May 2010) | 1 line Remove top-level 'General Questions' section, pushing up the questions it contains ........ r81567 | andrew.kuchling | 2010-05-27 16:29:59 -0500 (Thu, 27 May 2010) | 1 line Add item ........ r81593 | georg.brandl | 2010-05-29 03:46:18 -0500 (Sat, 29 May 2010) | 1 line #8616: add new turtle demo "nim". ........ r81635 | georg.brandl | 2010-06-01 02:25:23 -0500 (Tue, 01 Jun 2010) | 1 line Put docs for RegexObject.search() before RegexObject.match() to mirror re.search() and re.match() order. ........ r81680 | vinay.sajip | 2010-06-03 17:34:42 -0500 (Thu, 03 Jun 2010) | 1 line Issue #8890: Documentation changed to avoid reference to temporary files. ........ r81681 | sean.reifschneider | 2010-06-03 20:51:26 -0500 (Thu, 03 Jun 2010) | 2 lines Issue8810: Clearing up docstring for tzinfo.utcoffset. ........ r81684 | vinay.sajip | 2010-06-04 08:41:02 -0500 (Fri, 04 Jun 2010) | 1 line Issue #8890: Documentation changed to avoid reference to temporary files - other cases covered. ........ r81801 | andrew.kuchling | 2010-06-07 08:38:40 -0500 (Mon, 07 Jun 2010) | 1 line #8875: Remove duplicated paragraph ........ r81888 | andrew.kuchling | 2010-06-10 20:54:58 -0500 (Thu, 10 Jun 2010) | 1 line Add a few more items ........ r81931 | georg.brandl | 2010-06-12 01:26:54 -0500 (Sat, 12 Jun 2010) | 1 line Fix punctuation. ........ r81932 | georg.brandl | 2010-06-12 01:28:58 -0500 (Sat, 12 Jun 2010) | 1 line Document that an existing directory raises in mkdir(). ........ r81933 | georg.brandl | 2010-06-12 01:45:33 -0500 (Sat, 12 Jun 2010) | 1 line Update version in README. ........ r81939 | georg.brandl | 2010-06-12 04:45:01 -0500 (Sat, 12 Jun 2010) | 1 line Use newer toctree syntax. ........ r81940 | georg.brandl | 2010-06-12 04:45:28 -0500 (Sat, 12 Jun 2010) | 1 line Add document on how to build. ........ r81941 | georg.brandl | 2010-06-12 04:45:58 -0500 (Sat, 12 Jun 2010) | 1 line Fix gratuitous indentation. ........ r81942 | georg.brandl | 2010-06-12 04:46:03 -0500 (Sat, 12 Jun 2010) | 1 line Update README. ........ r81963 | andrew.kuchling | 2010-06-12 15:00:55 -0500 (Sat, 12 Jun 2010) | 1 line Grammar fix ........ r81984 | georg.brandl | 2010-06-14 10:58:39 -0500 (Mon, 14 Jun 2010) | 1 line #8993: fix reference. ........ r81991 | andrew.kuchling | 2010-06-14 19:38:58 -0500 (Mon, 14 Jun 2010) | 1 line Add another bunch of items ........ r82120 | andrew.kuchling | 2010-06-20 16:45:45 -0500 (Sun, 20 Jun 2010) | 1 line Note that Python 3.x isn't covered; add forward ref. for UTF-8; note error in 2.5 and up ........ r82188 | benjamin.peterson | 2010-06-23 19:02:46 -0500 (Wed, 23 Jun 2010) | 1 line remove reverted changed ........ r82264 | georg.brandl | 2010-06-27 05:47:47 -0500 (Sun, 27 Jun 2010) | 1 line Confusing punctuation. ........ r82265 | georg.brandl | 2010-06-27 05:49:23 -0500 (Sun, 27 Jun 2010) | 1 line Use designated syntax for optional grammar element. ........ r82266 | georg.brandl | 2010-06-27 05:51:44 -0500 (Sun, 27 Jun 2010) | 1 line Fix URL. ........ r82267 | georg.brandl | 2010-06-27 05:55:38 -0500 (Sun, 27 Jun 2010) | 1 line Two typos. ........
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the lookup of special methods that are called on instances, only in this
Merged revisions 80030,80067,80069,80080-80081,80084,80432-80433,80465-80470,81059,81065-81067 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r80030 | georg.brandl | 2010-04-13 08:43:54 +0200 (Di, 13 Apr 2010) | 1 line Get rid of multi-row cells. ........ r80067 | georg.brandl | 2010-04-14 10:53:38 +0200 (Mi, 14 Apr 2010) | 1 line #5341: typo. ........ r80069 | georg.brandl | 2010-04-14 15:50:31 +0200 (Mi, 14 Apr 2010) | 1 line Add an x-ref to where the O_ constants are documented and move the SEEK_ constants after lseek(). ........ r80080 | georg.brandl | 2010-04-14 21:16:38 +0200 (Mi, 14 Apr 2010) | 1 line #8399: add note about Windows and O_BINARY. ........ r80081 | georg.brandl | 2010-04-14 23:34:44 +0200 (Mi, 14 Apr 2010) | 1 line #5250: document __instancecheck__ and __subclasscheck__. I hope the part about the class/metaclass distinction is understandable. ........ r80084 | georg.brandl | 2010-04-14 23:46:45 +0200 (Mi, 14 Apr 2010) | 1 line Fix missing. ........ r80432 | georg.brandl | 2010-04-24 10:56:58 +0200 (Sa, 24 Apr 2010) | 1 line Markup fixes. ........ r80433 | georg.brandl | 2010-04-24 11:08:10 +0200 (Sa, 24 Apr 2010) | 1 line #7507: quote "!" in pipes.quote(); it is a special character for some shells. ........ r80465 | georg.brandl | 2010-04-25 12:29:17 +0200 (So, 25 Apr 2010) | 1 line Remove LaTeXy index entry syntax. ........ r80466 | georg.brandl | 2010-04-25 12:54:42 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Better cross-referencing in socket and winreg docs. ........ r80467 | georg.brandl | 2010-04-25 12:55:16 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Remove reference to winreg being the fabled high-level registry interface. ........ r80468 | georg.brandl | 2010-04-25 12:55:58 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Minor spelling changes to _winreg docs. ........ r80469 | georg.brandl | 2010-04-25 12:56:41 +0200 (So, 25 Apr 2010) | 1 line Fix code example to have valid syntax so that it can be highlighted. ........ r80470 | georg.brandl | 2010-04-25 12:57:15 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Make socket setblocking <-> settimeout examples symmetric. ........ r81059 | georg.brandl | 2010-05-10 23:02:51 +0200 (Mo, 10 Mai 2010) | 1 line #8642: fix wrong function name. ........ r81065 | georg.brandl | 2010-05-10 23:46:50 +0200 (Mo, 10 Mai 2010) | 1 line Fix reference direction. ........ r81066 | georg.brandl | 2010-05-10 23:50:57 +0200 (Mo, 10 Mai 2010) | 1 line Consolidate deprecation messages. ........ r81067 | georg.brandl | 2010-05-10 23:51:33 +0200 (Mo, 10 Mai 2010) | 1 line Fix typo. ........
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case the instance is itself a class.
.. seealso::
:pep:`3119` - Introducing Abstract Base Classes
Includes the specification for customizing :func:`isinstance` and
:func:`issubclass` behavior through :meth:`~class.__instancecheck__` and
:meth:`~class.__subclasscheck__`, with motivation for this functionality
in the context of adding Abstract Base Classes (see the :mod:`abc`
module) to the language.
Merged revisions 80030,80067,80069,80080-80081,80084,80432-80433,80465-80470,81059,81065-81067 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r80030 | georg.brandl | 2010-04-13 08:43:54 +0200 (Di, 13 Apr 2010) | 1 line Get rid of multi-row cells. ........ r80067 | georg.brandl | 2010-04-14 10:53:38 +0200 (Mi, 14 Apr 2010) | 1 line #5341: typo. ........ r80069 | georg.brandl | 2010-04-14 15:50:31 +0200 (Mi, 14 Apr 2010) | 1 line Add an x-ref to where the O_ constants are documented and move the SEEK_ constants after lseek(). ........ r80080 | georg.brandl | 2010-04-14 21:16:38 +0200 (Mi, 14 Apr 2010) | 1 line #8399: add note about Windows and O_BINARY. ........ r80081 | georg.brandl | 2010-04-14 23:34:44 +0200 (Mi, 14 Apr 2010) | 1 line #5250: document __instancecheck__ and __subclasscheck__. I hope the part about the class/metaclass distinction is understandable. ........ r80084 | georg.brandl | 2010-04-14 23:46:45 +0200 (Mi, 14 Apr 2010) | 1 line Fix missing. ........ r80432 | georg.brandl | 2010-04-24 10:56:58 +0200 (Sa, 24 Apr 2010) | 1 line Markup fixes. ........ r80433 | georg.brandl | 2010-04-24 11:08:10 +0200 (Sa, 24 Apr 2010) | 1 line #7507: quote "!" in pipes.quote(); it is a special character for some shells. ........ r80465 | georg.brandl | 2010-04-25 12:29:17 +0200 (So, 25 Apr 2010) | 1 line Remove LaTeXy index entry syntax. ........ r80466 | georg.brandl | 2010-04-25 12:54:42 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Better cross-referencing in socket and winreg docs. ........ r80467 | georg.brandl | 2010-04-25 12:55:16 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Remove reference to winreg being the fabled high-level registry interface. ........ r80468 | georg.brandl | 2010-04-25 12:55:58 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Minor spelling changes to _winreg docs. ........ r80469 | georg.brandl | 2010-04-25 12:56:41 +0200 (So, 25 Apr 2010) | 1 line Fix code example to have valid syntax so that it can be highlighted. ........ r80470 | georg.brandl | 2010-04-25 12:57:15 +0200 (So, 25 Apr 2010) | 1 line Patch from Tim Hatch: Make socket setblocking <-> settimeout examples symmetric. ........ r81059 | georg.brandl | 2010-05-10 23:02:51 +0200 (Mo, 10 Mai 2010) | 1 line #8642: fix wrong function name. ........ r81065 | georg.brandl | 2010-05-10 23:46:50 +0200 (Mo, 10 Mai 2010) | 1 line Fix reference direction. ........ r81066 | georg.brandl | 2010-05-10 23:50:57 +0200 (Mo, 10 Mai 2010) | 1 line Consolidate deprecation messages. ........ r81067 | georg.brandl | 2010-05-10 23:51:33 +0200 (Mo, 10 Mai 2010) | 1 line Fix typo. ........
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Emulating generic types
-----------------------
One can implement the generic class syntax as specified by :pep:`484`
(for example ``List[int]``) by defining a special method:
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.. classmethod:: object.__class_getitem__(cls, key)
Return an object representing the specialization of a generic class
by type arguments found in *key*.
This method is looked up on the class object itself, and when defined in
the class body, this method is implicitly a class method. Note, this
mechanism is primarily reserved for use with static type hints, other usage
is discouraged.
.. seealso::
:pep:`560` - Core support for typing module and generic types
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.. _callable-types:
Emulating callable objects
--------------------------
.. method:: object.__call__(self[, args...])
.. index:: pair: call; instance
Called when the instance is "called" as a function; if this method is defined,
``x(arg1, arg2, ...)`` roughly translates to ``type(x).__call__(x, arg1, ...)``.
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.. _sequence-types:
Emulating container types
-------------------------
The following methods can be defined to implement container objects. Containers
usually are sequences (such as lists or tuples) or mappings (like dictionaries),
but can represent other containers as well. The first set of methods is used
either to emulate a sequence or to emulate a mapping; the difference is that for
a sequence, the allowable keys should be the integers *k* for which ``0 <= k <
N`` where *N* is the length of the sequence, or slice objects, which define a
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range of items. It is also recommended that mappings provide the methods
:meth:`keys`, :meth:`values`, :meth:`items`, :meth:`get`, :meth:`clear`,
:meth:`setdefault`, :meth:`pop`, :meth:`popitem`, :meth:`!copy`, and
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:meth:`update` behaving similar to those for Python's standard dictionary
objects. The :mod:`collections.abc` module provides a
:class:`~collections.abc.MutableMapping`
abstract base class to help create those methods from a base set of
:meth:`__getitem__`, :meth:`__setitem__`, :meth:`__delitem__`, and :meth:`keys`.
Mutable sequences should provide methods :meth:`append`, :meth:`count`,
:meth:`index`, :meth:`extend`, :meth:`insert`, :meth:`pop`, :meth:`remove`,
:meth:`reverse` and :meth:`sort`, like Python standard list objects. Finally,
sequence types should implement addition (meaning concatenation) and
multiplication (meaning repetition) by defining the methods :meth:`__add__`,
:meth:`__radd__`, :meth:`__iadd__`, :meth:`__mul__`, :meth:`__rmul__` and
:meth:`__imul__` described below; they should not define other numerical
operators. It is recommended that both mappings and sequences implement the
:meth:`__contains__` method to allow efficient use of the ``in`` operator; for
mappings, ``in`` should search the mapping's keys; for sequences, it should
search through the values. It is further recommended that both mappings and
sequences implement the :meth:`__iter__` method to allow efficient iteration
through the container; for mappings, :meth:`__iter__` should iterate
through the object's keys; for sequences, it should iterate through the values.
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.. method:: object.__len__(self)
.. index::
builtin: len
single: __bool__() (object method)
Called to implement the built-in function :func:`len`. Should return the length
of the object, an integer ``>=`` 0. Also, an object that doesn't define a
:meth:`__bool__` method and whose :meth:`__len__` method returns zero is
considered to be false in a Boolean context.
.. impl-detail::
In CPython, the length is required to be at most :attr:`sys.maxsize`.
If the length is larger than :attr:`!sys.maxsize` some features (such as
:func:`len`) may raise :exc:`OverflowError`. To prevent raising
:exc:`!OverflowError` by truth value testing, an object must define a
:meth:`__bool__` method.
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.. method:: object.__length_hint__(self)
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Called to implement :func:`operator.length_hint`. Should return an estimated
length for the object (which may be greater or less than the actual length).
The length must be an integer ``>=`` 0. The return value may also be
:const:`NotImplemented`, which is treated the same as if the
``__length_hint__`` method didn't exist at all. This method is purely an
optimization and is never required for correctness.
.. versionadded:: 3.4
.. index:: object: slice
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.. note::
Slicing is done exclusively with the following three methods. A call like ::
a[1:2] = b
is translated to ::
a[slice(1, 2, None)] = b
and so forth. Missing slice items are always filled in with ``None``.
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.. method:: object.__getitem__(self, key)
Called to implement evaluation of ``self[key]``. For sequence types, the
accepted keys should be integers and slice objects. Note that the special
interpretation of negative indexes (if the class wishes to emulate a sequence
type) is up to the :meth:`__getitem__` method. If *key* is of an inappropriate
type, :exc:`TypeError` may be raised; if of a value outside the set of indexes
for the sequence (after any special interpretation of negative values),
:exc:`IndexError` should be raised. For mapping types, if *key* is missing (not
in the container), :exc:`KeyError` should be raised.
.. note::
:keyword:`for` loops expect that an :exc:`IndexError` will be raised for illegal
indexes to allow proper detection of the end of the sequence.
.. method:: object.__setitem__(self, key, value)
Called to implement assignment to ``self[key]``. Same note as for
:meth:`__getitem__`. This should only be implemented for mappings if the
objects support changes to the values for keys, or if new keys can be added, or
for sequences if elements can be replaced. The same exceptions should be raised
for improper *key* values as for the :meth:`__getitem__` method.
.. method:: object.__delitem__(self, key)
Called to implement deletion of ``self[key]``. Same note as for
:meth:`__getitem__`. This should only be implemented for mappings if the
objects support removal of keys, or for sequences if elements can be removed
from the sequence. The same exceptions should be raised for improper *key*
values as for the :meth:`__getitem__` method.
.. method:: object.__missing__(self, key)
Called by :class:`dict`\ .\ :meth:`__getitem__` to implement ``self[key]`` for dict subclasses
when key is not in the dictionary.
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.. method:: object.__iter__(self)
This method is called when an iterator is required for a container. This method
should return a new iterator object that can iterate over all the objects in the
container. For mappings, it should iterate over the keys of the container.
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Iterator objects also need to implement this method; they are required to return
themselves. For more information on iterator objects, see :ref:`typeiter`.
.. method:: object.__reversed__(self)
Called (if present) by the :func:`reversed` built-in to implement
reverse iteration. It should return a new iterator object that iterates
over all the objects in the container in reverse order.
If the :meth:`__reversed__` method is not provided, the :func:`reversed`
built-in will fall back to using the sequence protocol (:meth:`__len__` and
:meth:`__getitem__`). Objects that support the sequence protocol should
only provide :meth:`__reversed__` if they can provide an implementation
that is more efficient than the one provided by :func:`reversed`.
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The membership test operators (:keyword:`in` and :keyword:`not in`) are normally
implemented as an iteration through a container. However, container objects can
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supply the following special method with a more efficient implementation, which
also does not require the object be iterable.
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.. method:: object.__contains__(self, item)
Merged revisions 75365,75394,75402-75403,75418,75459,75484,75592-75596,75600,75602-75607,75610-75613,75616-75617,75623,75627,75640,75647,75696,75795 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r75365 | georg.brandl | 2009-10-11 22:16:16 +0200 (So, 11 Okt 2009) | 1 line Fix broken links found by "make linkcheck". scipy.org seems to be done right now, so I could not verify links going there. ........ r75394 | georg.brandl | 2009-10-13 20:10:59 +0200 (Di, 13 Okt 2009) | 1 line Fix markup. ........ r75402 | georg.brandl | 2009-10-14 17:51:48 +0200 (Mi, 14 Okt 2009) | 1 line #7125: fix typo. ........ r75403 | georg.brandl | 2009-10-14 17:57:46 +0200 (Mi, 14 Okt 2009) | 1 line #7126: os.environ changes *do* take effect in subprocesses started with os.system(). ........ r75418 | georg.brandl | 2009-10-14 20:48:32 +0200 (Mi, 14 Okt 2009) | 1 line #7116: str.join() takes an iterable. ........ r75459 | georg.brandl | 2009-10-17 10:57:43 +0200 (Sa, 17 Okt 2009) | 1 line Fix refleaks in _ctypes PyCSimpleType_New, which fixes the refleak seen in test___all__. ........ r75484 | georg.brandl | 2009-10-18 09:58:12 +0200 (So, 18 Okt 2009) | 1 line Fix missing word. ........ r75592 | georg.brandl | 2009-10-22 09:05:48 +0200 (Do, 22 Okt 2009) | 1 line Fix punctuation. ........ r75593 | georg.brandl | 2009-10-22 09:06:49 +0200 (Do, 22 Okt 2009) | 1 line Revert unintended change. ........ r75594 | georg.brandl | 2009-10-22 09:56:02 +0200 (Do, 22 Okt 2009) | 1 line Fix markup. ........ r75595 | georg.brandl | 2009-10-22 09:56:56 +0200 (Do, 22 Okt 2009) | 1 line Fix duplicate target. ........ r75596 | georg.brandl | 2009-10-22 10:05:04 +0200 (Do, 22 Okt 2009) | 1 line Add a new directive marking up implementation details and start using it. ........ r75600 | georg.brandl | 2009-10-22 13:01:46 +0200 (Do, 22 Okt 2009) | 1 line Make it more robust. ........ r75602 | georg.brandl | 2009-10-22 13:28:06 +0200 (Do, 22 Okt 2009) | 1 line Document new directive. ........ r75603 | georg.brandl | 2009-10-22 13:28:23 +0200 (Do, 22 Okt 2009) | 1 line Allow short form with text as argument. ........ r75604 | georg.brandl | 2009-10-22 13:36:50 +0200 (Do, 22 Okt 2009) | 1 line Fix stylesheet for multi-paragraph impl-details. ........ r75605 | georg.brandl | 2009-10-22 13:48:10 +0200 (Do, 22 Okt 2009) | 1 line Use "impl-detail" directive where applicable. ........ r75606 | georg.brandl | 2009-10-22 17:00:06 +0200 (Do, 22 Okt 2009) | 1 line #6324: membership test tries iteration via __iter__. ........ r75607 | georg.brandl | 2009-10-22 17:04:09 +0200 (Do, 22 Okt 2009) | 1 line #7088: document new functions in signal as Unix-only. ........ r75610 | georg.brandl | 2009-10-22 17:27:24 +0200 (Do, 22 Okt 2009) | 1 line Reorder __slots__ fine print and add a clarification. ........ r75611 | georg.brandl | 2009-10-22 17:42:32 +0200 (Do, 22 Okt 2009) | 1 line #7035: improve docs of the various <method>_errors() functions, and give them docstrings. ........ r75612 | georg.brandl | 2009-10-22 17:52:15 +0200 (Do, 22 Okt 2009) | 1 line #7156: document curses as Unix-only. ........ r75613 | georg.brandl | 2009-10-22 17:54:35 +0200 (Do, 22 Okt 2009) | 1 line #6977: getopt does not support optional option arguments. ........ r75616 | georg.brandl | 2009-10-22 18:17:05 +0200 (Do, 22 Okt 2009) | 1 line Add proper references. ........ r75617 | georg.brandl | 2009-10-22 18:20:55 +0200 (Do, 22 Okt 2009) | 1 line Make printout margin important. ........ r75623 | georg.brandl | 2009-10-23 10:14:44 +0200 (Fr, 23 Okt 2009) | 1 line #7188: fix optionxform() docs. ........ r75627 | fred.drake | 2009-10-23 15:04:51 +0200 (Fr, 23 Okt 2009) | 2 lines add further note about what's passed to optionxform ........ r75640 | neil.schemenauer | 2009-10-23 21:58:17 +0200 (Fr, 23 Okt 2009) | 2 lines Improve some docstrings in the 'warnings' module. ........ r75647 | georg.brandl | 2009-10-24 12:04:19 +0200 (Sa, 24 Okt 2009) | 1 line Fix markup. ........ r75696 | georg.brandl | 2009-10-25 21:25:43 +0100 (So, 25 Okt 2009) | 1 line Fix a demo. ........ r75795 | georg.brandl | 2009-10-27 16:10:22 +0100 (Di, 27 Okt 2009) | 1 line Fix a strange mis-edit. ........
2009-10-27 12:28:25 -03:00
Called to implement membership test operators. Should return true if *item*
is in *self*, false otherwise. For mapping objects, this should consider the
keys of the mapping rather than the values or the key-item pairs.
For objects that don't define :meth:`__contains__`, the membership test first
tries iteration via :meth:`__iter__`, then the old sequence iteration
protocol via :meth:`__getitem__`, see :ref:`this section in the language
reference <membership-test-details>`.
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.. _numeric-types:
Emulating numeric types
-----------------------
The following methods can be defined to emulate numeric objects. Methods
corresponding to operations that are not supported by the particular kind of
number implemented (e.g., bitwise operations for non-integral numbers) should be
left undefined.
.. method:: object.__add__(self, other)
object.__sub__(self, other)
object.__mul__(self, other)
object.__matmul__(self, other)
object.__truediv__(self, other)
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object.__floordiv__(self, other)
object.__mod__(self, other)
object.__divmod__(self, other)
object.__pow__(self, other[, modulo])
object.__lshift__(self, other)
object.__rshift__(self, other)
object.__and__(self, other)
object.__xor__(self, other)
object.__or__(self, other)
.. index::
builtin: divmod
builtin: pow
builtin: pow
These methods are called to implement the binary arithmetic operations
(``+``, ``-``, ``*``, ``@``, ``/``, ``//``, ``%``, :func:`divmod`,
:func:`pow`, ``**``, ``<<``, ``>>``, ``&``, ``^``, ``|``). For instance, to
evaluate the expression ``x + y``, where *x* is an instance of a class that
has an :meth:`__add__` method, ``type(x).__add__(x, y)`` is called. The
:meth:`__divmod__` method should be the equivalent to using
:meth:`__floordiv__` and :meth:`__mod__`; it should not be related to
:meth:`__truediv__`. Note that :meth:`__pow__` should be defined to accept
an optional third argument if the ternary version of the built-in :func:`pow`
function is to be supported.
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If one of those methods does not support the operation with the supplied
arguments, it should return ``NotImplemented``.
.. method:: object.__radd__(self, other)
object.__rsub__(self, other)
object.__rmul__(self, other)
object.__rmatmul__(self, other)
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object.__rtruediv__(self, other)
object.__rfloordiv__(self, other)
object.__rmod__(self, other)
object.__rdivmod__(self, other)
object.__rpow__(self, other[, modulo])
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object.__rlshift__(self, other)
object.__rrshift__(self, other)
object.__rand__(self, other)
object.__rxor__(self, other)
object.__ror__(self, other)
.. index::
builtin: divmod
builtin: pow
These methods are called to implement the binary arithmetic operations
(``+``, ``-``, ``*``, ``@``, ``/``, ``//``, ``%``, :func:`divmod`,
:func:`pow`, ``**``, ``<<``, ``>>``, ``&``, ``^``, ``|``) with reflected
(swapped) operands. These functions are only called if the left operand does
not support the corresponding operation [#]_ and the operands are of different
types. [#]_ For instance, to evaluate the expression ``x - y``, where *y* is
an instance of a class that has an :meth:`__rsub__` method,
``type(y).__rsub__(y, x)`` is called if ``type(x).__sub__(x, y)`` returns
*NotImplemented*.
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.. index:: builtin: pow
Note that ternary :func:`pow` will not try calling :meth:`__rpow__` (the
coercion rules would become too complicated).
.. note::
If the right operand's type is a subclass of the left operand's type and
that subclass provides a different implementation of the reflected method
for the operation, this method will be called before the left operand's
non-reflected method. This behavior allows subclasses to override their
ancestors' operations.
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.. method:: object.__iadd__(self, other)
object.__isub__(self, other)
object.__imul__(self, other)
object.__imatmul__(self, other)
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object.__itruediv__(self, other)
object.__ifloordiv__(self, other)
object.__imod__(self, other)
object.__ipow__(self, other[, modulo])
object.__ilshift__(self, other)
object.__irshift__(self, other)
object.__iand__(self, other)
object.__ixor__(self, other)
object.__ior__(self, other)
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These methods are called to implement the augmented arithmetic assignments
(``+=``, ``-=``, ``*=``, ``@=``, ``/=``, ``//=``, ``%=``, ``**=``, ``<<=``,
``>>=``, ``&=``, ``^=``, ``|=``). These methods should attempt to do the
operation in-place (modifying *self*) and return the result (which could be,
but does not have to be, *self*). If a specific method is not defined, the
augmented assignment falls back to the normal methods. For instance, if *x*
is an instance of a class with an :meth:`__iadd__` method, ``x += y`` is
equivalent to ``x = x.__iadd__(y)`` . Otherwise, ``x.__add__(y)`` and
``y.__radd__(x)`` are considered, as with the evaluation of ``x + y``. In
certain situations, augmented assignment can result in unexpected errors (see
:ref:`faq-augmented-assignment-tuple-error`), but this behavior is in fact
part of the data model.
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.. method:: object.__neg__(self)
object.__pos__(self)
object.__abs__(self)
object.__invert__(self)
.. index:: builtin: abs
Called to implement the unary arithmetic operations (``-``, ``+``, :func:`abs`
and ``~``).
.. method:: object.__complex__(self)
object.__int__(self)
object.__float__(self)
.. index::
builtin: complex
builtin: int
builtin: float
Called to implement the built-in functions :func:`complex`,
:func:`int` and :func:`float`. Should return a value
of the appropriate type.
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.. method:: object.__index__(self)
Called to implement :func:`operator.index`, and whenever Python needs to
losslessly convert the numeric object to an integer object (such as in
slicing, or in the built-in :func:`bin`, :func:`hex` and :func:`oct`
functions). Presence of this method indicates that the numeric object is
an integer type. Must return an integer.
If :meth:`__int__`, :meth:`__float__` and :meth:`__complex__` are not
defined then corresponding built-in functions :func:`int`, :func:`float`
and :func:`complex` fall back to :meth:`__index__`.
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.. method:: object.__round__(self, [,ndigits])
object.__trunc__(self)
object.__floor__(self)
object.__ceil__(self)
.. index:: builtin: round
Called to implement the built-in function :func:`round` and :mod:`math`
functions :func:`~math.trunc`, :func:`~math.floor` and :func:`~math.ceil`.
Unless *ndigits* is passed to :meth:`!__round__` all these methods should
return the value of the object truncated to an :class:`~numbers.Integral`
(typically an :class:`int`).
If :meth:`__int__` is not defined then the built-in function :func:`int`
falls back to :meth:`__trunc__`.
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.. _context-managers:
With Statement Context Managers
-------------------------------
A :dfn:`context manager` is an object that defines the runtime context to be
established when executing a :keyword:`with` statement. The context manager
handles the entry into, and the exit from, the desired runtime context for the
execution of the block of code. Context managers are normally invoked using the
:keyword:`!with` statement (described in section :ref:`with`), but can also be
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used by directly invoking their methods.
.. index::
statement: with
single: context manager
Typical uses of context managers include saving and restoring various kinds of
global state, locking and unlocking resources, closing opened files, etc.
For more information on context managers, see :ref:`typecontextmanager`.
.. method:: object.__enter__(self)
Enter the runtime context related to this object. The :keyword:`with` statement
will bind this method's return value to the target(s) specified in the
:keyword:`!as` clause of the statement, if any.
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.. method:: object.__exit__(self, exc_type, exc_value, traceback)
Exit the runtime context related to this object. The parameters describe the
exception that caused the context to be exited. If the context was exited
without an exception, all three arguments will be :const:`None`.
If an exception is supplied, and the method wishes to suppress the exception
(i.e., prevent it from being propagated), it should return a true value.
Otherwise, the exception will be processed normally upon exit from this method.
Note that :meth:`__exit__` methods should not reraise the passed-in exception;
this is the caller's responsibility.
.. seealso::
:pep:`343` - The "with" statement
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The specification, background, and examples for the Python :keyword:`with`
statement.
.. _class-pattern-matching:
Customizing positional arguments in class pattern matching
----------------------------------------------------------
When using a class name in a pattern, positional arguments in the pattern are not
allowed by default, i.e. ``case MyClass(x, y)`` is typically invalid without special
support in ``MyClass``. To be able to use that kind of patterns, the class needs to
define a *__match_args__* attribute.
.. data:: object.__match_args__
This class variable can be assigned a tuple of strings. When this class is
used in a class pattern with positional arguments, each positional argument will
be converted into a keyword argument, using the corresponding value in
*__match_args__* as the keyword. The absence of this attribute is equivalent to
setting it to ``()``.
For example, if ``MyClass.__match_args__`` is ``("left", "center", "right")`` that means
that ``case MyClass(x, y)`` is equivalent to ``case MyClass(left=x, center=y)``. Note
that the number of arguments in the pattern must be smaller than or equal to the number
of elements in *__match_args__*; if it is larger, the pattern match attempt will raise
a :exc:`TypeError`.
.. versionadded:: 3.10
.. seealso::
:pep:`634` - Structural Pattern Matching
The specification for the Python ``match`` statement.
.. _special-lookup:
Special method lookup
---------------------
For custom classes, implicit invocations of special methods are only guaranteed
to work correctly if defined on an object's type, not in the object's instance
dictionary. That behaviour is the reason why the following code raises an
exception::
>>> class C:
... pass
...
>>> c = C()
>>> c.__len__ = lambda: 5
>>> len(c)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: object of type 'C' has no len()
The rationale behind this behaviour lies with a number of special methods such
as :meth:`__hash__` and :meth:`__repr__` that are implemented by all objects,
including type objects. If the implicit lookup of these methods used the
conventional lookup process, they would fail when invoked on the type object
itself::
>>> 1 .__hash__() == hash(1)
True
>>> int.__hash__() == hash(int)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: descriptor '__hash__' of 'int' object needs an argument
Incorrectly attempting to invoke an unbound method of a class in this way is
sometimes referred to as 'metaclass confusion', and is avoided by bypassing
the instance when looking up special methods::
>>> type(1).__hash__(1) == hash(1)
True
>>> type(int).__hash__(int) == hash(int)
True
In addition to bypassing any instance attributes in the interest of
Merged revisions 67531-67532,67538,67553-67554,67556-67557,67571,67574-67575,67579-67580,67591,67597,67608,67631 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r67531 | georg.brandl | 2008-12-04 19:54:05 +0100 (Thu, 04 Dec 2008) | 2 lines Add reference to enumerate() to indices example. ........ r67532 | georg.brandl | 2008-12-04 19:59:16 +0100 (Thu, 04 Dec 2008) | 2 lines Add another heapq example. ........ r67538 | georg.brandl | 2008-12-04 22:28:16 +0100 (Thu, 04 Dec 2008) | 2 lines Clarification to avoid confusing output with file descriptors. ........ r67553 | georg.brandl | 2008-12-05 08:49:49 +0100 (Fri, 05 Dec 2008) | 2 lines #4408: document regex.groups. ........ r67554 | georg.brandl | 2008-12-05 08:52:26 +0100 (Fri, 05 Dec 2008) | 2 lines #4409: fix asterisks looking like footnotes. ........ r67556 | georg.brandl | 2008-12-05 09:02:17 +0100 (Fri, 05 Dec 2008) | 2 lines #4441: improve doc for os.open() flags. ........ r67557 | georg.brandl | 2008-12-05 09:06:57 +0100 (Fri, 05 Dec 2008) | 2 lines Add an index entry for "subclassing immutable types". ........ r67571 | georg.brandl | 2008-12-05 10:13:45 +0100 (Fri, 05 Dec 2008) | 2 lines Use markup. ........ r67574 | georg.brandl | 2008-12-05 10:25:32 +0100 (Fri, 05 Dec 2008) | 2 lines #4441 followup: Add link to open() docs for Windows. ........ r67575 | georg.brandl | 2008-12-05 12:34:51 +0100 (Fri, 05 Dec 2008) | 2 lines #4544: add `dedent` to textwrap.__all__. ........ r67579 | georg.brandl | 2008-12-05 16:29:39 +0100 (Fri, 05 Dec 2008) | 2 lines #4517: add "special method" glossary entry and clarify when __getattribute__ is bypassed. ........ r67580 | georg.brandl | 2008-12-05 16:32:29 +0100 (Fri, 05 Dec 2008) | 2 lines #4478: document that copyfile() can raise Error. ........ r67591 | georg.brandl | 2008-12-05 19:00:06 +0100 (Fri, 05 Dec 2008) | 2 lines Followup to #4511: add link from decorator glossary entry to definition. ........ r67597 | georg.brandl | 2008-12-05 20:03:19 +0100 (Fri, 05 Dec 2008) | 2 lines Remove confusing sentence part. ........ r67608 | georg.brandl | 2008-12-06 12:57:12 +0100 (Sat, 06 Dec 2008) | 2 lines Follow-up to #4488: document PIPE and STDOUT properly. ........ r67631 | georg.brandl | 2008-12-07 12:54:07 +0100 (Sun, 07 Dec 2008) | 2 lines Add link to the favicon to the docs. ........
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correctness, implicit special method lookup generally also bypasses the
:meth:`__getattribute__` method even of the object's metaclass::
>>> class Meta(type):
... def __getattribute__(*args):
... print("Metaclass getattribute invoked")
... return type.__getattribute__(*args)
...
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>>> class C(object, metaclass=Meta):
... def __len__(self):
... return 10
... def __getattribute__(*args):
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... print("Class getattribute invoked")
... return object.__getattribute__(*args)
...
>>> c = C()
>>> c.__len__() # Explicit lookup via instance
Class getattribute invoked
10
>>> type(c).__len__(c) # Explicit lookup via type
Metaclass getattribute invoked
10
>>> len(c) # Implicit lookup
10
Bypassing the :meth:`__getattribute__` machinery in this fashion
provides significant scope for speed optimisations within the
interpreter, at the cost of some flexibility in the handling of
special methods (the special method *must* be set on the class
object itself in order to be consistently invoked by the interpreter).
.. index::
single: coroutine
Coroutines
==========
Awaitable Objects
-----------------
An :term:`awaitable` object generally implements an :meth:`__await__` method.
:term:`Coroutine objects <coroutine>` returned from :keyword:`async def` functions
are awaitable.
.. note::
The :term:`generator iterator` objects returned from generators
decorated with :func:`types.coroutine`
are also awaitable, but they do not implement :meth:`__await__`.
.. method:: object.__await__(self)
Must return an :term:`iterator`. Should be used to implement
:term:`awaitable` objects. For instance, :class:`asyncio.Future` implements
this method to be compatible with the :keyword:`await` expression.
.. versionadded:: 3.5
.. seealso:: :pep:`492` for additional information about awaitable objects.
.. _coroutine-objects:
Coroutine Objects
-----------------
:term:`Coroutine objects <coroutine>` are :term:`awaitable` objects.
A coroutine's execution can be controlled by calling :meth:`__await__` and
iterating over the result. When the coroutine has finished executing and
returns, the iterator raises :exc:`StopIteration`, and the exception's
:attr:`~StopIteration.value` attribute holds the return value. If the
coroutine raises an exception, it is propagated by the iterator. Coroutines
should not directly raise unhandled :exc:`StopIteration` exceptions.
Coroutines also have the methods listed below, which are analogous to
those of generators (see :ref:`generator-methods`). However, unlike
generators, coroutines do not directly support iteration.
.. versionchanged:: 3.5.2
It is a :exc:`RuntimeError` to await on a coroutine more than once.
.. method:: coroutine.send(value)
Starts or resumes execution of the coroutine. If *value* is ``None``,
this is equivalent to advancing the iterator returned by
:meth:`__await__`. If *value* is not ``None``, this method delegates
to the :meth:`~generator.send` method of the iterator that caused
the coroutine to suspend. The result (return value,
:exc:`StopIteration`, or other exception) is the same as when
iterating over the :meth:`__await__` return value, described above.
.. method:: coroutine.throw(type[, value[, traceback]])
Raises the specified exception in the coroutine. This method delegates
to the :meth:`~generator.throw` method of the iterator that caused
the coroutine to suspend, if it has such a method. Otherwise,
the exception is raised at the suspension point. The result
(return value, :exc:`StopIteration`, or other exception) is the same as
when iterating over the :meth:`__await__` return value, described
above. If the exception is not caught in the coroutine, it propagates
back to the caller.
.. method:: coroutine.close()
Causes the coroutine to clean itself up and exit. If the coroutine
is suspended, this method first delegates to the :meth:`~generator.close`
method of the iterator that caused the coroutine to suspend, if it
has such a method. Then it raises :exc:`GeneratorExit` at the
suspension point, causing the coroutine to immediately clean itself up.
Finally, the coroutine is marked as having finished executing, even if
it was never started.
Coroutine objects are automatically closed using the above process when
they are about to be destroyed.
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.. _async-iterators:
Asynchronous Iterators
----------------------
An *asynchronous iterator* can call asynchronous code in
its ``__anext__`` method.
Asynchronous iterators can be used in an :keyword:`async for` statement.
.. method:: object.__aiter__(self)
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Must return an *asynchronous iterator* object.
.. method:: object.__anext__(self)
Must return an *awaitable* resulting in a next value of the iterator. Should
raise a :exc:`StopAsyncIteration` error when the iteration is over.
An example of an asynchronous iterable object::
class Reader:
async def readline(self):
...
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def __aiter__(self):
return self
async def __anext__(self):
val = await self.readline()
if val == b'':
raise StopAsyncIteration
return val
.. versionadded:: 3.5
.. versionchanged:: 3.7
Prior to Python 3.7, ``__aiter__`` could return an *awaitable*
that would resolve to an
:term:`asynchronous iterator <asynchronous iterator>`.
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Starting with Python 3.7, ``__aiter__`` must return an
asynchronous iterator object. Returning anything else
will result in a :exc:`TypeError` error.
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.. _async-context-managers:
Asynchronous Context Managers
-----------------------------
An *asynchronous context manager* is a *context manager* that is able to
suspend execution in its ``__aenter__`` and ``__aexit__`` methods.
Asynchronous context managers can be used in an :keyword:`async with` statement.
.. method:: object.__aenter__(self)
Semantically similar to :meth:`__enter__`, the only
difference being that it must return an *awaitable*.
.. method:: object.__aexit__(self, exc_type, exc_value, traceback)
Semantically similar to :meth:`__exit__`, the only
difference being that it must return an *awaitable*.
An example of an asynchronous context manager class::
class AsyncContextManager:
async def __aenter__(self):
await log('entering context')
async def __aexit__(self, exc_type, exc, tb):
await log('exiting context')
.. versionadded:: 3.5
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.. rubric:: Footnotes
.. [#] It *is* possible in some cases to change an object's type, under certain
controlled conditions. It generally isn't a good idea though, since it can
lead to some very strange behaviour if it is handled incorrectly.
.. [#] The :meth:`__hash__`, :meth:`__iter__`, :meth:`__reversed__`, and
:meth:`__contains__` methods have special handling for this; others
will still raise a :exc:`TypeError`, but may do so by relying on
the behavior that ``None`` is not callable.
.. [#] "Does not support" here means that the class has no such method, or
the method returns ``NotImplemented``. Do not set the method to
``None`` if you want to force fallback to the right operand's reflected
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method—that will instead have the opposite effect of explicitly
*blocking* such fallback.
.. [#] For operands of the same type, it is assumed that if the non-reflected
method -- such as :meth:`__add__` -- fails then the overall operation is not
supported, which is why the reflected method is not called.