cpython/Doc/library/string.rst

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:mod:`string` --- Common string operations
==========================================
.. module:: string
:synopsis: Common string operations.
**Source code:** :source:`Lib/string.py`
--------------
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.. seealso::
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:ref:`textseq`
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:ref:`string-methods`
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String constants
----------------
The constants defined in this module are:
.. data:: ascii_letters
The concatenation of the :const:`ascii_lowercase` and :const:`ascii_uppercase`
constants described below. This value is not locale-dependent.
.. data:: ascii_lowercase
The lowercase letters ``'abcdefghijklmnopqrstuvwxyz'``. This value is not
locale-dependent and will not change.
.. data:: ascii_uppercase
The uppercase letters ``'ABCDEFGHIJKLMNOPQRSTUVWXYZ'``. This value is not
locale-dependent and will not change.
.. data:: digits
The string ``'0123456789'``.
.. data:: hexdigits
The string ``'0123456789abcdefABCDEF'``.
.. data:: octdigits
The string ``'01234567'``.
.. data:: punctuation
String of ASCII characters which are considered punctuation characters
in the ``C`` locale: ``!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~``.
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.. data:: printable
String of ASCII characters which are considered printable. This is a
combination of :const:`digits`, :const:`ascii_letters`, :const:`punctuation`,
and :const:`whitespace`.
.. data:: whitespace
A string containing all ASCII characters that are considered whitespace.
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This includes the characters space, tab, linefeed, return, formfeed, and
vertical tab.
.. _string-formatting:
Custom String Formatting
------------------------
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The built-in string class provides the ability to do complex variable
substitutions and value formatting via the :meth:`~str.format` method described in
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:pep:`3101`. The :class:`Formatter` class in the :mod:`string` module allows
you to create and customize your own string formatting behaviors using the same
implementation as the built-in :meth:`~str.format` method.
Merged revisions 76847,76851,76869,76882,76891-76892,76924,77007,77070,77092,77096,77120,77126,77155 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r76847 | benjamin.peterson | 2009-12-14 21:25:27 -0600 (Mon, 14 Dec 2009) | 1 line adverb ........ r76851 | benjamin.peterson | 2009-12-15 21:28:52 -0600 (Tue, 15 Dec 2009) | 1 line remove lib2to3 resource ........ r76869 | vinay.sajip | 2009-12-17 08:52:00 -0600 (Thu, 17 Dec 2009) | 1 line Issue #7529: logging: Minor correction to documentation. ........ r76882 | georg.brandl | 2009-12-19 11:30:28 -0600 (Sat, 19 Dec 2009) | 1 line #7527: use standard versionadded tags. ........ r76891 | georg.brandl | 2009-12-19 12:16:31 -0600 (Sat, 19 Dec 2009) | 1 line #7479: add note about function availability on Unices. ........ r76892 | georg.brandl | 2009-12-19 12:20:18 -0600 (Sat, 19 Dec 2009) | 1 line #7480: remove tautology. ........ r76924 | georg.brandl | 2009-12-20 08:28:05 -0600 (Sun, 20 Dec 2009) | 1 line Small indentation fix. ........ r77007 | gregory.p.smith | 2009-12-23 03:31:11 -0600 (Wed, 23 Dec 2009) | 3 lines Fix possible integer overflow in lchown and fchown functions. For issue1747858. ........ r77070 | amaury.forgeotdarc | 2009-12-27 14:06:44 -0600 (Sun, 27 Dec 2009) | 2 lines Fix a typo in comment ........ r77092 | georg.brandl | 2009-12-28 02:48:24 -0600 (Mon, 28 Dec 2009) | 1 line #7404: remove reference to non-existing example files. ........ r77096 | benjamin.peterson | 2009-12-28 14:51:17 -0600 (Mon, 28 Dec 2009) | 1 line document new fix_callable behavior ........ r77120 | georg.brandl | 2009-12-29 15:09:17 -0600 (Tue, 29 Dec 2009) | 1 line #7595: fix typo in argument default constant. ........ r77126 | amaury.forgeotdarc | 2009-12-29 17:06:17 -0600 (Tue, 29 Dec 2009) | 2 lines #7579: Add docstrings to the msvcrt module ........ r77155 | georg.brandl | 2009-12-30 13:03:00 -0600 (Wed, 30 Dec 2009) | 1 line We only support Windows NT derivatives now. ........
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.. class:: Formatter
The :class:`Formatter` class has the following public methods:
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.. method:: format(format_string, *args, **kwargs)
The primary API method. It takes a format string and
an arbitrary set of positional and keyword arguments.
It is just a wrapper that calls :meth:`vformat`.
.. versionchanged:: 3.7
A format string argument is now :ref:`positional-only
<positional-only_parameter>`.
.. method:: vformat(format_string, args, kwargs)
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This function does the actual work of formatting. It is exposed as a
separate function for cases where you want to pass in a predefined
dictionary of arguments, rather than unpacking and repacking the
dictionary as individual arguments using the ``*args`` and ``**kwargs``
syntax. :meth:`vformat` does the work of breaking up the format string
into character data and replacement fields. It calls the various
methods described below.
In addition, the :class:`Formatter` defines a number of methods that are
intended to be replaced by subclasses:
.. method:: parse(format_string)
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Loop over the format_string and return an iterable of tuples
(*literal_text*, *field_name*, *format_spec*, *conversion*). This is used
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by :meth:`vformat` to break the string into either literal text, or
replacement fields.
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The values in the tuple conceptually represent a span of literal text
followed by a single replacement field. If there is no literal text
(which can happen if two replacement fields occur consecutively), then
*literal_text* will be a zero-length string. If there is no replacement
field, then the values of *field_name*, *format_spec* and *conversion*
will be ``None``.
.. method:: get_field(field_name, args, kwargs)
Given *field_name* as returned by :meth:`parse` (see above), convert it to
an object to be formatted. Returns a tuple (obj, used_key). The default
version takes strings of the form defined in :pep:`3101`, such as
"0[name]" or "label.title". *args* and *kwargs* are as passed in to
:meth:`vformat`. The return value *used_key* has the same meaning as the
*key* parameter to :meth:`get_value`.
.. method:: get_value(key, args, kwargs)
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Retrieve a given field value. The *key* argument will be either an
integer or a string. If it is an integer, it represents the index of the
positional argument in *args*; if it is a string, then it represents a
named argument in *kwargs*.
The *args* parameter is set to the list of positional arguments to
:meth:`vformat`, and the *kwargs* parameter is set to the dictionary of
keyword arguments.
For compound field names, these functions are only called for the first
component of the field name; Subsequent components are handled through
normal attribute and indexing operations.
So for example, the field expression '0.name' would cause
:meth:`get_value` to be called with a *key* argument of 0. The ``name``
attribute will be looked up after :meth:`get_value` returns by calling the
built-in :func:`getattr` function.
If the index or keyword refers to an item that does not exist, then an
:exc:`IndexError` or :exc:`KeyError` should be raised.
.. method:: check_unused_args(used_args, args, kwargs)
Implement checking for unused arguments if desired. The arguments to this
function is the set of all argument keys that were actually referred to in
the format string (integers for positional arguments, and strings for
named arguments), and a reference to the *args* and *kwargs* that was
passed to vformat. The set of unused args can be calculated from these
parameters. :meth:`check_unused_args` is assumed to raise an exception if
the check fails.
.. method:: format_field(value, format_spec)
:meth:`format_field` simply calls the global :func:`format` built-in. The
method is provided so that subclasses can override it.
.. method:: convert_field(value, conversion)
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Converts the value (returned by :meth:`get_field`) given a conversion type
(as in the tuple returned by the :meth:`parse` method). The default
version understands 's' (str), 'r' (repr) and 'a' (ascii) conversion
types.
.. _formatstrings:
Format String Syntax
--------------------
The :meth:`str.format` method and the :class:`Formatter` class share the same
syntax for format strings (although in the case of :class:`Formatter`,
subclasses can define their own format string syntax). The syntax is
related to that of :ref:`formatted string literals <f-strings>`, but
there are differences.
.. index::
single: {} (curly brackets); in string formatting
single: . (dot); in string formatting
single: [] (square brackets); in string formatting
single: ! (exclamation); in string formatting
single: : (colon); in string formatting
Format strings contain "replacement fields" surrounded by curly braces ``{}``.
Anything that is not contained in braces is considered literal text, which is
copied unchanged to the output. If you need to include a brace character in the
literal text, it can be escaped by doubling: ``{{`` and ``}}``.
The grammar for a replacement field is as follows:
.. productionlist:: sf
replacement_field: "{" [`field_name`] ["!" `conversion`] [":" `format_spec`] "}"
field_name: arg_name ("." `attribute_name` | "[" `element_index` "]")*
arg_name: [`identifier` | `digit`+]
attribute_name: `identifier`
element_index: `digit`+ | `index_string`
index_string: <any source character except "]"> +
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conversion: "r" | "s" | "a"
format_spec: <described in the next section>
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In less formal terms, the replacement field can start with a *field_name* that specifies
the object whose value is to be formatted and inserted
into the output instead of the replacement field.
The *field_name* is optionally followed by a *conversion* field, which is
preceded by an exclamation point ``'!'``, and a *format_spec*, which is preceded
by a colon ``':'``. These specify a non-default format for the replacement value.
See also the :ref:`formatspec` section.
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The *field_name* itself begins with an *arg_name* that is either a number or a
keyword. If it's a number, it refers to a positional argument, and if it's a keyword,
it refers to a named keyword argument. If the numerical arg_names in a format string
are 0, 1, 2, ... in sequence, they can all be omitted (not just some)
and the numbers 0, 1, 2, ... will be automatically inserted in that order.
Because *arg_name* is not quote-delimited, it is not possible to specify arbitrary
dictionary keys (e.g., the strings ``'10'`` or ``':-]'``) within a format string.
The *arg_name* can be followed by any number of index or
attribute expressions. An expression of the form ``'.name'`` selects the named
attribute using :func:`getattr`, while an expression of the form ``'[index]'``
does an index lookup using :func:`__getitem__`.
.. versionchanged:: 3.1
The positional argument specifiers can be omitted for :meth:`str.format`,
so ``'{} {}'.format(a, b)`` is equivalent to ``'{0} {1}'.format(a, b)``.
.. versionchanged:: 3.4
The positional argument specifiers can be omitted for :class:`Formatter`.
Some simple format string examples::
"First, thou shalt count to {0}" # References first positional argument
"Bring me a {}" # Implicitly references the first positional argument
"From {} to {}" # Same as "From {0} to {1}"
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.
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The *conversion* field causes a type coercion before formatting. Normally, the
job of formatting a value is done by the :meth:`__format__` method of the value
itself. However, in some cases it is desirable to force a type to be formatted
as a string, overriding its own definition of formatting. By converting the
value to a string before calling :meth:`__format__`, the normal formatting logic
is bypassed.
Three conversion flags are currently supported: ``'!s'`` which calls :func:`str`
on the value, ``'!r'`` which calls :func:`repr` and ``'!a'`` which calls
:func:`ascii`.
Some examples::
"Harold's a clever {0!s}" # Calls str() on the argument first
"Bring out the holy {name!r}" # Calls repr() on the argument first
"More {!a}" # Calls ascii() on the argument first
The *format_spec* field contains a specification of how the value should be
presented, including such details as field width, alignment, padding, decimal
precision and so on. Each value type can define its own "formatting
mini-language" or interpretation of the *format_spec*.
Most built-in types support a common formatting mini-language, which is
described in the next section.
A *format_spec* field can also include nested replacement fields within it.
These nested replacement fields may contain a field name, conversion flag
and format specification, but deeper nesting is
not allowed. The replacement fields within the
format_spec are substituted before the *format_spec* string is interpreted.
This allows the formatting of a value to be dynamically specified.
See the :ref:`formatexamples` section for some examples.
.. _formatspec:
Format Specification Mini-Language
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"Format specifications" are used within replacement fields contained within a
format string to define how individual values are presented (see
:ref:`formatstrings` and :ref:`f-strings`).
They can also be passed directly to the built-in
:func:`format` function. Each formattable type may define how the format
specification is to be interpreted.
Most built-in types implement the following options for format specifications,
although some of the formatting options are only supported by the numeric types.
A general convention is that an empty format string (``""``) produces
the same result as if you had called :func:`str` on the value. A
non-empty format string typically modifies the result.
The general form of a *standard format specifier* is:
.. productionlist:: sf
format_spec: [[`fill`]`align`][`sign`][#][0][`width`][`grouping_option`][.`precision`][`type`]
fill: <any character>
align: "<" | ">" | "=" | "^"
sign: "+" | "-" | " "
width: `digit`+
grouping_option: "_" | ","
precision: `digit`+
type: "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
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If a valid *align* value is specified, it can be preceded by a *fill*
character that can be any character and defaults to a space if omitted.
It is not possible to use a literal curly brace ("``{``" or "``}``") as
the *fill* character in a :ref:`formatted string literal
<f-strings>` or when using the :meth:`str.format`
method. However, it is possible to insert a curly brace
with a nested replacement field. This limitation doesn't
affect the :func:`format` function.
The meaning of the various alignment options is as follows:
.. index::
single: < (less); in string formatting
single: > (greater); in string formatting
single: = (equals); in string formatting
single: ^ (caret); in string formatting
+---------+----------------------------------------------------------+
| Option | Meaning |
+=========+==========================================================+
| ``'<'`` | Forces the field to be left-aligned within the available |
| | space (this is the default for most objects). |
+---------+----------------------------------------------------------+
| ``'>'`` | Forces the field to be right-aligned within the |
| | available space (this is the default for numbers). |
+---------+----------------------------------------------------------+
| ``'='`` | Forces the padding to be placed after the sign (if any) |
| | but before the digits. This is used for printing fields |
| | in the form '+000000120'. This alignment option is only |
| | valid for numeric types. It becomes the default when '0'|
| | immediately precedes the field width. |
+---------+----------------------------------------------------------+
| ``'^'`` | Forces the field to be centered within the available |
| | space. |
+---------+----------------------------------------------------------+
Note that unless a minimum field width is defined, the field width will always
be the same size as the data to fill it, so that the alignment option has no
meaning in this case.
The *sign* option is only valid for number types, and can be one of the
following:
.. index::
single: + (plus); in string formatting
single: - (minus); in string formatting
single: space; in string formatting
+---------+----------------------------------------------------------+
| Option | Meaning |
+=========+==========================================================+
| ``'+'`` | indicates that a sign should be used for both |
| | positive as well as negative numbers. |
+---------+----------------------------------------------------------+
| ``'-'`` | indicates that a sign should be used only for negative |
| | numbers (this is the default behavior). |
+---------+----------------------------------------------------------+
| space | indicates that a leading space should be used on |
| | positive numbers, and a minus sign on negative numbers. |
+---------+----------------------------------------------------------+
.. index:: single: # (hash); in string formatting
The ``'#'`` option causes the "alternate form" to be used for the
conversion. The alternate form is defined differently for different
types. This option is only valid for integer, float, complex and
Decimal types. For integers, when binary, octal, or hexadecimal output
is used, this option adds the prefix respective ``'0b'``, ``'0o'``, or
``'0x'`` to the output value. For floats, complex and Decimal the
alternate form causes the result of the conversion to always contain a
decimal-point character, even if no digits follow it. Normally, a
decimal-point character appears in the result of these conversions
only if a digit follows it. In addition, for ``'g'`` and ``'G'``
conversions, trailing zeros are not removed from the result.
.. index:: single: , (comma); in string formatting
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The ``','`` option signals the use of a comma for a thousands separator.
For a locale aware separator, use the ``'n'`` integer presentation type
instead.
.. versionchanged:: 3.1
Added the ``','`` option (see also :pep:`378`).
.. index:: single: _ (underscore); in string formatting
The ``'_'`` option signals the use of an underscore for a thousands
separator for floating point presentation types and for integer
presentation type ``'d'``. For integer presentation types ``'b'``,
``'o'``, ``'x'``, and ``'X'``, underscores will be inserted every 4
digits. For other presentation types, specifying this option is an
error.
.. versionchanged:: 3.6
Added the ``'_'`` option (see also :pep:`515`).
*width* is a decimal integer defining the minimum field width. If not
specified, then the field width will be determined by the content.
When no explicit alignment is given, preceding the *width* field by a zero
(``'0'``) character enables
sign-aware zero-padding for numeric types. This is equivalent to a *fill*
character of ``'0'`` with an *alignment* type of ``'='``.
The *precision* is a decimal number indicating how many digits should be
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 ........
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displayed after the decimal point for a floating point value formatted with
``'f'`` and ``'F'``, or before and after the decimal point for a floating point
value formatted with ``'g'`` or ``'G'``. For non-number types the field
indicates the maximum field size - in other words, how many characters will be
used from the field content. The *precision* is not allowed for integer values.
Finally, the *type* determines how the data should be presented.
The available string presentation types are:
+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
| ``'s'`` | String format. This is the default type for strings and |
| | may be omitted. |
+---------+----------------------------------------------------------+
| None | The same as ``'s'``. |
+---------+----------------------------------------------------------+
The available integer presentation types are:
+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
| ``'b'`` | Binary format. Outputs the number in base 2. |
+---------+----------------------------------------------------------+
| ``'c'`` | Character. Converts the integer to the corresponding |
| | unicode character before printing. |
+---------+----------------------------------------------------------+
| ``'d'`` | Decimal Integer. Outputs the number in base 10. |
+---------+----------------------------------------------------------+
| ``'o'`` | Octal format. Outputs the number in base 8. |
+---------+----------------------------------------------------------+
| ``'x'`` | Hex format. Outputs the number in base 16, using |
| | lower-case letters for the digits above 9. |
+---------+----------------------------------------------------------+
| ``'X'`` | Hex format. Outputs the number in base 16, using |
| | upper-case letters for the digits above 9. |
+---------+----------------------------------------------------------+
| ``'n'`` | Number. This is the same as ``'d'``, except that it uses |
| | the current locale setting to insert the appropriate |
| | number separator characters. |
+---------+----------------------------------------------------------+
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 ........
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| None | The same as ``'d'``. |
+---------+----------------------------------------------------------+
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In addition to the above presentation types, integers can be formatted
with the floating point presentation types listed below (except
``'n'`` and ``None``). When doing so, :func:`float` is used to convert the
integer to a floating point number before formatting.
The available presentation types for floating point and decimal values are:
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+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
| ``'e'`` | Exponent notation. Prints the number in scientific |
| | notation using the letter 'e' to indicate the exponent. |
| | The default precision is ``6``. |
+---------+----------------------------------------------------------+
| ``'E'`` | Exponent notation. Same as ``'e'`` except it uses an |
| | upper case 'E' as the separator character. |
+---------+----------------------------------------------------------+
| ``'f'`` | Fixed-point notation. Displays the number as a |
| | fixed-point number. The default precision is ``6``. |
+---------+----------------------------------------------------------+
| ``'F'`` | Fixed-point notation. Same as ``'f'``, but converts |
| | ``nan`` to ``NAN`` and ``inf`` to ``INF``. |
+---------+----------------------------------------------------------+
| ``'g'`` | General format. For a given precision ``p >= 1``, |
| | this rounds the number to ``p`` significant digits and |
| | then formats the result in either fixed-point format |
| | or in scientific notation, depending on its magnitude. |
| | |
| | The precise rules are as follows: suppose that the |
| | result formatted with presentation type ``'e'`` and |
| | precision ``p-1`` would have exponent ``exp``. Then |
| | if ``-4 <= exp < p``, the number is formatted |
| | with presentation type ``'f'`` and precision |
| | ``p-1-exp``. Otherwise, the number is formatted |
| | with presentation type ``'e'`` and precision ``p-1``. |
| | In both cases insignificant trailing zeros are removed |
| | from the significand, and the decimal point is also |
| | removed if there are no remaining digits following it. |
| | |
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| | Positive and negative infinity, positive and negative |
| | zero, and nans, are formatted as ``inf``, ``-inf``, |
| | ``0``, ``-0`` and ``nan`` respectively, regardless of |
| | the precision. |
| | |
| | A precision of ``0`` is treated as equivalent to a |
| | precision of ``1``. The default precision is ``6``. |
+---------+----------------------------------------------------------+
| ``'G'`` | General format. Same as ``'g'`` except switches to |
| | ``'E'`` if the number gets too large. The |
| | representations of infinity and NaN are uppercased, too. |
+---------+----------------------------------------------------------+
| ``'n'`` | Number. This is the same as ``'g'``, except that it uses |
| | the current locale setting to insert the appropriate |
| | number separator characters. |
+---------+----------------------------------------------------------+
| ``'%'`` | Percentage. Multiplies the number by 100 and displays |
| | in fixed (``'f'``) format, followed by a percent sign. |
+---------+----------------------------------------------------------+
| None | Similar to ``'g'``, except that fixed-point notation, |
| | when used, has at least one digit past the decimal point.|
| | The default precision is as high as needed to represent |
| | the particular value. The overall effect is to match the |
| | output of :func:`str` as altered by the other format |
| | modifiers. |
+---------+----------------------------------------------------------+
.. _formatexamples:
Format examples
^^^^^^^^^^^^^^^
This section contains examples of the :meth:`str.format` syntax and
comparison with the old ``%``-formatting.
In most of the cases the syntax is similar to the old ``%``-formatting, with the
addition of the ``{}`` and with ``:`` used instead of ``%``.
For example, ``'%03.2f'`` can be translated to ``'{:03.2f}'``.
The new format syntax also supports new and different options, shown in the
following examples.
Accessing arguments by position::
>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
>>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+ only
'a, b, c'
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad') # arguments' indices can be repeated
'abracadabra'
Accessing arguments by name::
>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)
'Coordinates: 37.24N, -115.81W'
Accessing arguments' attributes::
>>> c = 3-5j
>>> ('The complex number {0} is formed from the real part {0.real} '
... 'and the imaginary part {0.imag}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point:
... def __init__(self, x, y):
... self.x, self.y = x, y
... def __str__(self):
... return 'Point({self.x}, {self.y})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)'
Accessing arguments' items::
>>> coord = (3, 5)
>>> 'X: {0[0]}; Y: {0[1]}'.format(coord)
'X: 3; Y: 5'
Replacing ``%s`` and ``%r``::
>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"
Aligning the text and specifying a width::
>>> '{:<30}'.format('left aligned')
'left aligned '
>>> '{:>30}'.format('right aligned')
' right aligned'
>>> '{:^30}'.format('centered')
' centered '
>>> '{:*^30}'.format('centered') # use '*' as a fill char
'***********centered***********'
Replacing ``%+f``, ``%-f``, and ``% f`` and specifying a sign::
>>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it always
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14) # show a space for positive numbers
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'
Replacing ``%x`` and ``%o`` and converting the value to different bases::
>>> # format also supports binary numbers
>>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}".format(42)
'int: 42; hex: 2a; oct: 52; bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42)
'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'
Using the comma as a thousands separator::
>>> '{:,}'.format(1234567890)
'1,234,567,890'
Expressing a percentage::
>>> points = 19
>>> total = 22
>>> 'Correct answers: {:.2%}'.format(points/total)
'Correct answers: 86.36%'
Using type-specific formatting::
>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'
Nesting arguments and more complex examples::
>>> for align, text in zip('<^>', ['left', 'center', 'right']):
... '{0:{fill}{align}16}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12): #doctest: +NORMALIZE_WHITESPACE
... for base in 'dXob':
... print('{0:{width}{base}}'.format(num, base=base, width=width), end=' ')
... print()
...
5 5 5 101
6 6 6 110
7 7 7 111
8 8 10 1000
9 9 11 1001
10 A 12 1010
11 B 13 1011
.. _template-strings:
2007-08-15 11:28:22 -03:00
Template strings
----------------
Template strings provide simpler string substitutions as described in
:pep:`292`. A primary use case for template strings is for
internationalization (i18n) since in that context, the simpler syntax and
functionality makes it easier to translate than other built-in string
formatting facilities in Python. As an example of a library built on template
strings for i18n, see the
`flufl.i18n <http://flufli18n.readthedocs.io/en/latest/>`_ package.
.. index:: single: $ (dollar); in template strings
Template strings support ``$``-based substitutions, using the following rules:
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* ``$$`` is an escape; it is replaced with a single ``$``.
* ``$identifier`` names a substitution placeholder matching a mapping key of
``"identifier"``. By default, ``"identifier"`` is restricted to any
case-insensitive ASCII alphanumeric string (including underscores) that
starts with an underscore or ASCII letter. The first non-identifier
character after the ``$`` character terminates this placeholder
specification.
* ``${identifier}`` is equivalent to ``$identifier``. It is required when
valid identifier characters follow the placeholder but are not part of the
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placeholder, such as ``"${noun}ification"``.
Any other appearance of ``$`` in the string will result in a :exc:`ValueError`
being raised.
The :mod:`string` module provides a :class:`Template` class that implements
these rules. The methods of :class:`Template` are:
.. class:: Template(template)
The constructor takes a single argument which is the template string.
.. method:: substitute(mapping, **kwds)
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Performs the template substitution, returning a new string. *mapping* is
any dictionary-like object with keys that match the placeholders in the
template. Alternatively, you can provide keyword arguments, where the
keywords are the placeholders. When both *mapping* and *kwds* are given
and there are duplicates, the placeholders from *kwds* take precedence.
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.. method:: safe_substitute(mapping, **kwds)
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Like :meth:`substitute`, except that if placeholders are missing from
*mapping* and *kwds*, instead of raising a :exc:`KeyError` exception, the
original placeholder will appear in the resulting string intact. Also,
unlike with :meth:`substitute`, any other appearances of the ``$`` will
simply return ``$`` instead of raising :exc:`ValueError`.
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While other exceptions may still occur, this method is called "safe"
because it always tries to return a usable string instead of
raising an exception. In another sense, :meth:`safe_substitute` may be
anything other than safe, since it will silently ignore malformed
templates containing dangling delimiters, unmatched braces, or
placeholders that are not valid Python identifiers.
2007-08-15 11:28:22 -03:00
Merged revisions 76259,76326,76376-76377,76430,76471,76517 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ................ r76259 | georg.brandl | 2009-11-14 05:50:51 -0600 (Sat, 14 Nov 2009) | 1 line Fix terminology. ................ r76326 | georg.brandl | 2009-11-16 10:44:05 -0600 (Mon, 16 Nov 2009) | 1 line #7302: fix link. ................ r76376 | georg.brandl | 2009-11-18 13:39:14 -0600 (Wed, 18 Nov 2009) | 1 line upcase Python ................ r76377 | georg.brandl | 2009-11-18 14:05:15 -0600 (Wed, 18 Nov 2009) | 1 line Fix markup. ................ r76430 | r.david.murray | 2009-11-20 07:29:43 -0600 (Fri, 20 Nov 2009) | 2 lines Issue 7363: fix indentation in socketserver udpserver example. ................ r76471 | georg.brandl | 2009-11-23 13:53:19 -0600 (Mon, 23 Nov 2009) | 1 line #7345: fix arguments of formatyear(). ................ r76517 | benjamin.peterson | 2009-11-25 12:16:46 -0600 (Wed, 25 Nov 2009) | 29 lines Merged revisions 76160-76161,76250,76252,76447,76506 via svnmerge from svn+ssh://pythondev@svn.python.org/sandbox/trunk/2to3/lib2to3 ........ r76160 | benjamin.peterson | 2009-11-08 18:53:48 -0600 (Sun, 08 Nov 2009) | 1 line undeprecate the -p option; it's useful for converting python3 sources ........ r76161 | benjamin.peterson | 2009-11-08 19:05:37 -0600 (Sun, 08 Nov 2009) | 1 line simplify condition ........ r76250 | benjamin.peterson | 2009-11-13 16:56:48 -0600 (Fri, 13 Nov 2009) | 1 line fix handling of a utf-8 bom #7313 ........ r76252 | benjamin.peterson | 2009-11-13 16:58:36 -0600 (Fri, 13 Nov 2009) | 1 line remove pdb turd ........ r76447 | benjamin.peterson | 2009-11-22 18:17:40 -0600 (Sun, 22 Nov 2009) | 1 line #7375 fix nested transformations in fix_urllib ........ r76506 | benjamin.peterson | 2009-11-24 18:34:31 -0600 (Tue, 24 Nov 2009) | 1 line use generator expressions in any() ........ ................
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:class:`Template` instances also provide one public data attribute:
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Merged revisions 76259,76326,76376-76377,76430,76471,76517 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ................ r76259 | georg.brandl | 2009-11-14 05:50:51 -0600 (Sat, 14 Nov 2009) | 1 line Fix terminology. ................ r76326 | georg.brandl | 2009-11-16 10:44:05 -0600 (Mon, 16 Nov 2009) | 1 line #7302: fix link. ................ r76376 | georg.brandl | 2009-11-18 13:39:14 -0600 (Wed, 18 Nov 2009) | 1 line upcase Python ................ r76377 | georg.brandl | 2009-11-18 14:05:15 -0600 (Wed, 18 Nov 2009) | 1 line Fix markup. ................ r76430 | r.david.murray | 2009-11-20 07:29:43 -0600 (Fri, 20 Nov 2009) | 2 lines Issue 7363: fix indentation in socketserver udpserver example. ................ r76471 | georg.brandl | 2009-11-23 13:53:19 -0600 (Mon, 23 Nov 2009) | 1 line #7345: fix arguments of formatyear(). ................ r76517 | benjamin.peterson | 2009-11-25 12:16:46 -0600 (Wed, 25 Nov 2009) | 29 lines Merged revisions 76160-76161,76250,76252,76447,76506 via svnmerge from svn+ssh://pythondev@svn.python.org/sandbox/trunk/2to3/lib2to3 ........ r76160 | benjamin.peterson | 2009-11-08 18:53:48 -0600 (Sun, 08 Nov 2009) | 1 line undeprecate the -p option; it's useful for converting python3 sources ........ r76161 | benjamin.peterson | 2009-11-08 19:05:37 -0600 (Sun, 08 Nov 2009) | 1 line simplify condition ........ r76250 | benjamin.peterson | 2009-11-13 16:56:48 -0600 (Fri, 13 Nov 2009) | 1 line fix handling of a utf-8 bom #7313 ........ r76252 | benjamin.peterson | 2009-11-13 16:58:36 -0600 (Fri, 13 Nov 2009) | 1 line remove pdb turd ........ r76447 | benjamin.peterson | 2009-11-22 18:17:40 -0600 (Sun, 22 Nov 2009) | 1 line #7375 fix nested transformations in fix_urllib ........ r76506 | benjamin.peterson | 2009-11-24 18:34:31 -0600 (Tue, 24 Nov 2009) | 1 line use generator expressions in any() ........ ................
2009-11-25 14:34:42 -04:00
.. attribute:: template
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This is the object passed to the constructor's *template* argument. In
general, you shouldn't change it, but read-only access is not enforced.
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Here is an example of how to use a Template::
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>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
'tim likes kung pao'
>>> d = dict(who='tim')
>>> Template('Give $who $100').substitute(d)
Traceback (most recent call last):
...
ValueError: Invalid placeholder in string: line 1, col 11
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>>> Template('$who likes $what').substitute(d)
Traceback (most recent call last):
...
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KeyError: 'what'
>>> Template('$who likes $what').safe_substitute(d)
'tim likes $what'
Advanced usage: you can derive subclasses of :class:`Template` to customize
the placeholder syntax, delimiter character, or the entire regular expression
used to parse template strings. To do this, you can override these class
attributes:
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* *delimiter* -- This is the literal string describing a placeholder
introducing delimiter. The default value is ``$``. Note that this should
*not* be a regular expression, as the implementation will call
:meth:`re.escape` on this string as needed. Note further that you cannot
change the delimiter after class creation (i.e. a different delimiter must
be set in the subclass's class namespace).
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* *idpattern* -- This is the regular expression describing the pattern for
non-braced placeholders. The default value is the regular expression
``(?a:[_a-z][_a-z0-9]*)``. If this is given and *braceidpattern* is
``None`` this pattern will also apply to braced placeholders.
.. note::
Since default *flags* is ``re.IGNORECASE``, pattern ``[a-z]`` can match
with some non-ASCII characters. That's why we use the local ``a`` flag
here.
.. versionchanged:: 3.7
*braceidpattern* can be used to define separate patterns used inside and
outside the braces.
* *braceidpattern* -- This is like *idpattern* but describes the pattern for
braced placeholders. Defaults to ``None`` which means to fall back to
*idpattern* (i.e. the same pattern is used both inside and outside braces).
If given, this allows you to define different patterns for braced and
unbraced placeholders.
.. versionadded:: 3.7
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* *flags* -- The regular expression flags that will be applied when compiling
the regular expression used for recognizing substitutions. The default value
is ``re.IGNORECASE``. Note that ``re.VERBOSE`` will always be added to the
flags, so custom *idpattern*\ s must follow conventions for verbose regular
expressions.
.. versionadded:: 3.2
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Alternatively, you can provide the entire regular expression pattern by
overriding the class attribute *pattern*. If you do this, the value must be a
regular expression object with four named capturing groups. The capturing
groups correspond to the rules given above, along with the invalid placeholder
rule:
* *escaped* -- This group matches the escape sequence, e.g. ``$$``, in the
default pattern.
* *named* -- This group matches the unbraced placeholder name; it should not
include the delimiter in capturing group.
* *braced* -- This group matches the brace enclosed placeholder name; it should
not include either the delimiter or braces in the capturing group.
* *invalid* -- This group matches any other delimiter pattern (usually a single
delimiter), and it should appear last in the regular expression.
Helper functions
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----------------
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.. function:: capwords(s, sep=None)
Split the argument into words using :meth:`str.split`, capitalize each word
using :meth:`str.capitalize`, and join the capitalized words using
:meth:`str.join`. If the optional second argument *sep* is absent
or ``None``, runs of whitespace characters are replaced by a single space
and leading and trailing whitespace are removed, otherwise *sep* is used to
split and join the words.