cpython/Doc/reference/compound_stmts.rst

639 lines
24 KiB
ReStructuredText
Raw Normal View History

2007-08-15 11:28:22 -03:00
.. _compound:
*******************
Compound statements
*******************
.. index:: pair: compound; statement
Compound statements contain (groups of) other statements; they affect or control
the execution of those other statements in some way. In general, compound
statements span multiple lines, although in simple incarnations a whole compound
statement may be contained in one line.
The :keyword:`if`, :keyword:`while` and :keyword:`for` statements implement
traditional control flow constructs. :keyword:`try` specifies exception
handlers and/or cleanup code for a group of statements, while the
:keyword:`with` statement allows the execution of initialization and
finalization code around a block of code. Function and class definitions are
also syntactically compound statements.
2007-08-15 11:28:22 -03:00
.. index::
single: clause
single: suite
Compound statements consist of one or more 'clauses.' A clause consists of a
header and a 'suite.' The clause headers of a particular compound statement are
all at the same indentation level. Each clause header begins with a uniquely
identifying keyword and ends with a colon. A suite is a group of statements
controlled by a clause. A suite can be one or more semicolon-separated simple
statements on the same line as the header, following the header's colon, or it
can be one or more indented statements on subsequent lines. Only the latter
form of suite can contain nested compound statements; the following is illegal,
mostly because it wouldn't be clear to which :keyword:`if` clause a following
:keyword:`else` clause would belong::
2007-08-15 11:28:22 -03:00
if test1: if test2: print(x)
2007-08-15 11:28:22 -03:00
Also note that the semicolon binds tighter than the colon in this context, so
that in the following example, either all or none of the :func:`print` calls are
executed::
2007-08-15 11:28:22 -03:00
if x < y < z: print(x); print(y); print(z)
2007-08-15 11:28:22 -03:00
Summarizing:
.. productionlist::
compound_stmt: `if_stmt`
: | `while_stmt`
: | `for_stmt`
: | `try_stmt`
: | `with_stmt`
: | `funcdef`
: | `classdef`
suite: `stmt_list` NEWLINE | NEWLINE INDENT `statement`+ DEDENT
statement: `stmt_list` NEWLINE | `compound_stmt`
stmt_list: `simple_stmt` (";" `simple_stmt`)* [";"]
.. index::
single: NEWLINE token
single: DEDENT token
pair: dangling; else
Note that statements always end in a ``NEWLINE`` possibly followed by a
``DEDENT``. Also note that optional continuation clauses always begin with a
2007-08-15 11:28:22 -03:00
keyword that cannot start a statement, thus there are no ambiguities (the
'dangling :keyword:`else`' problem is solved in Python by requiring nested
:keyword:`if` statements to be indented).
The formatting of the grammar rules in the following sections places each clause
on a separate line for clarity.
.. _if:
.. _elif:
.. _else:
2007-08-15 11:28:22 -03:00
The :keyword:`if` statement
===========================
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
.. index::
statement: if
keyword: elif
keyword: else
keyword: elif
keyword: else
2007-08-15 11:28:22 -03:00
The :keyword:`if` statement is used for conditional execution:
.. productionlist::
if_stmt: "if" `expression` ":" `suite`
: ( "elif" `expression` ":" `suite` )*
: ["else" ":" `suite`]
It selects exactly one of the suites by evaluating the expressions one by one
until one is found to be true (see section :ref:`booleans` for the definition of
true and false); then that suite is executed (and no other part of the
:keyword:`if` statement is executed or evaluated). If all expressions are
false, the suite of the :keyword:`else` clause, if present, is executed.
.. _while:
The :keyword:`while` statement
==============================
.. index::
statement: while
keyword: else
2007-08-15 11:28:22 -03:00
pair: loop; statement
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
keyword: else
2007-08-15 11:28:22 -03:00
The :keyword:`while` statement is used for repeated execution as long as an
expression is true:
.. productionlist::
while_stmt: "while" `expression` ":" `suite`
: ["else" ":" `suite`]
This repeatedly tests the expression and, if it is true, executes the first
suite; if the expression is false (which may be the first time it is tested) the
suite of the :keyword:`else` clause, if present, is executed and the loop
terminates.
.. index::
statement: break
statement: continue
A :keyword:`break` statement executed in the first suite terminates the loop
without executing the :keyword:`else` clause's suite. A :keyword:`continue`
statement executed in the first suite skips the rest of the suite and goes back
to testing the expression.
.. _for:
The :keyword:`for` statement
============================
.. index::
statement: for
keyword: in
keyword: else
pair: target; list
2007-08-15 11:28:22 -03:00
pair: loop; statement
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
keyword: in
keyword: else
pair: target; list
object: sequence
2007-08-15 11:28:22 -03:00
The :keyword:`for` statement is used to iterate over the elements of a sequence
(such as a string, tuple or list) or other iterable object:
.. productionlist::
for_stmt: "for" `target_list` "in" `expression_list` ":" `suite`
: ["else" ":" `suite`]
The expression list is evaluated once; it should yield an iterable object. An
iterator is created for the result of the ``expression_list``. The suite is
then executed once for each item provided by the iterator, in the order of
ascending indices. Each item in turn is assigned to the target list using the
standard rules for assignments (see :ref:`assignment`), and then the suite is
executed. When the items are exhausted (which is immediately when the sequence
is empty or an iterator raises a :exc:`StopIteration` exception), the suite in
2007-08-15 11:28:22 -03:00
the :keyword:`else` clause, if present, is executed, and the loop terminates.
.. index::
statement: break
statement: continue
A :keyword:`break` statement executed in the first suite terminates the loop
without executing the :keyword:`else` clause's suite. A :keyword:`continue`
statement executed in the first suite skips the rest of the suite and continues
with the next item, or with the :keyword:`else` clause if there was no next
item.
The suite may assign to the variable(s) in the target list; this does not affect
the next item assigned to it.
.. index::
builtin: range
Names in the target list are not deleted when the loop is finished, but if the
sequence is empty, it will not have been assigned to at all by the loop. Hint:
the built-in function :func:`range` returns an iterator of integers suitable to
2009-06-03 00:13:30 -03:00
emulate the effect of Pascal's ``for i := a to b do``; e.g., ``list(range(3))``
returns the list ``[0, 1, 2]``.
2007-08-15 11:28:22 -03:00
.. note::
2007-08-15 11:28:22 -03:00
.. index::
single: loop; over mutable sequence
single: mutable sequence; loop over
There is a subtlety when the sequence is being modified by the loop (this can
only occur for mutable sequences, i.e. lists). An internal counter is used
to keep track of which item is used next, and this is incremented on each
2007-08-15 11:28:22 -03:00
iteration. When this counter has reached the length of the sequence the loop
terminates. This means that if the suite deletes the current (or a previous)
item from the sequence, the next item will be skipped (since it gets the
index of the current item which has already been treated). Likewise, if the
suite inserts an item in the sequence before the current item, the current
item will be treated again the next time through the loop. This can lead to
nasty bugs that can be avoided by making a temporary copy using a slice of
the whole sequence, e.g., ::
2007-08-15 11:28:22 -03:00
for x in a[:]:
if x < 0: a.remove(x)
2007-08-15 11:28:22 -03:00
.. _try:
.. _except:
.. _finally:
2007-08-15 11:28:22 -03:00
The :keyword:`try` statement
============================
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
.. index::
statement: try
keyword: except
keyword: finally
.. index:: keyword: except
2007-08-15 11:28:22 -03:00
The :keyword:`try` statement specifies exception handlers and/or cleanup code
for a group of statements:
.. productionlist::
try_stmt: try1_stmt | try2_stmt
try1_stmt: "try" ":" `suite`
2007-09-06 11:03:41 -03:00
: ("except" [`expression` ["as" `target`]] ":" `suite`)+
2007-08-15 11:28:22 -03:00
: ["else" ":" `suite`]
: ["finally" ":" `suite`]
try2_stmt: "try" ":" `suite`
: "finally" ":" `suite`
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
The :keyword:`except` clause(s) specify one or more exception handlers. When no
2007-08-15 11:28:22 -03:00
exception occurs in the :keyword:`try` clause, no exception handler is executed.
When an exception occurs in the :keyword:`try` suite, a search for an exception
handler is started. This search inspects the except clauses in turn until one
is found that matches the exception. An expression-less except clause, if
present, must be last; it matches any exception. For an except clause with an
expression, that expression is evaluated, and the clause matches the exception
if the resulting object is "compatible" with the exception. An object is
compatible with an exception if it is the class or a base class of the exception
object or a tuple containing an item compatible with the exception.
If no except clause matches the exception, the search for an exception handler
continues in the surrounding code and on the invocation stack. [#]_
If the evaluation of an expression in the header of an except clause raises an
exception, the original search for a handler is canceled and a search starts for
the new exception in the surrounding code and on the call stack (it is treated
as if the entire :keyword:`try` statement raised the exception).
When a matching except clause is found, the exception is assigned to the target
specified after the :keyword:`as` keyword in that except clause, if present, and
the except clause's suite is executed. All except clauses must have an
executable block. When the end of this block is reached, execution continues
normally after the entire try statement. (This means that if two nested
handlers exist for the same exception, and the exception occurs in the try
clause of the inner handler, the outer handler will not handle the exception.)
When an exception has been assigned using ``as target``, it is cleared at the
end of the except clause. This is as if ::
except E as N:
foo
was translated to ::
except E as N:
try:
foo
finally:
del N
2010-06-28 22:27:35 -03:00
This means the exception must be assigned to a different name to be able to
refer to it after the except clause. Exceptions are cleared because with the
traceback attached to them, they form a reference cycle with the stack frame,
keeping all locals in that frame alive until the next garbage collection occurs.
2007-08-15 11:28:22 -03:00
.. index::
module: sys
object: traceback
Before an except clause's suite is executed, details about the exception are
stored in the :mod:`sys` module and can be access via :func:`sys.exc_info`.
:func:`sys.exc_info` returns a 3-tuple consisting of the exception class, the
exception instance and a traceback object (see section :ref:`types`) identifying
the point in the program where the exception occurred. :func:`sys.exc_info`
values are restored to their previous values (before the call) when returning
from a function that handled an exception.
2007-08-15 11:28:22 -03:00
.. index::
keyword: else
statement: return
statement: break
statement: continue
The optional :keyword:`else` clause is executed if and when control flows off
the end of the :keyword:`try` clause. [#]_ Exceptions in the :keyword:`else`
clause are not handled by the preceding :keyword:`except` clauses.
.. index:: keyword: finally
If :keyword:`finally` is present, it specifies a 'cleanup' handler. The
:keyword:`try` clause is executed, including any :keyword:`except` and
:keyword:`else` clauses. If an exception occurs in any of the clauses and is
not handled, the exception is temporarily saved. The :keyword:`finally` clause
is executed. If there is a saved exception, it is re-raised at the end of the
:keyword:`finally` clause. If the :keyword:`finally` clause raises another
exception or executes a :keyword:`return` or :keyword:`break` statement, the
saved exception is set as the context of the new exception. The exception
information is not available to the program during execution of the
:keyword:`finally` clause.
2007-08-15 11:28:22 -03:00
.. index::
statement: return
statement: break
statement: continue
When a :keyword:`return`, :keyword:`break` or :keyword:`continue` statement is
executed in the :keyword:`try` suite of a :keyword:`try`...\ :keyword:`finally`
statement, the :keyword:`finally` clause is also executed 'on the way out.' A
:keyword:`continue` statement is illegal in the :keyword:`finally` clause. (The
reason is a problem with the current implementation --- this restriction may be
lifted in the future).
Additional information on exceptions can be found in section :ref:`exceptions`,
and information on using the :keyword:`raise` statement to generate exceptions
may be found in section :ref:`raise`.
.. _with:
.. _as:
2007-08-15 11:28:22 -03:00
The :keyword:`with` statement
=============================
.. index:: statement: with
The :keyword:`with` statement is used to wrap the execution of a block with
methods defined by a context manager (see section :ref:`context-managers`).
This allows common :keyword:`try`...\ :keyword:`except`...\ :keyword:`finally`
usage patterns to be encapsulated for convenient reuse.
2007-08-15 11:28:22 -03:00
.. productionlist::
with_stmt: "with" with_item ("," with_item)* ":" `suite`
with_item: `expression` ["as" `target`]
2007-08-15 11:28:22 -03:00
The execution of the :keyword:`with` statement with one "item" proceeds as follows:
2007-08-15 11:28:22 -03:00
#. The context expression (the expression given in the :token:`with_item`) is
evaluated to obtain a context manager.
2007-08-15 11:28:22 -03:00
#. The context manager's :meth:`__exit__` is loaded for later use.
2007-08-15 11:28:22 -03:00
#. The context manager's :meth:`__enter__` method is invoked.
#. If a target was included in the :keyword:`with` statement, the return value
from :meth:`__enter__` is assigned to it.
.. note::
The :keyword:`with` statement guarantees that if the :meth:`__enter__`
method returns without an error, then :meth:`__exit__` will always be
called. Thus, if an error occurs during the assignment to the target list,
it will be treated the same as an error occurring within the suite would
be. See step 6 below.
2007-08-15 11:28:22 -03:00
#. The suite is executed.
#. The context manager's :meth:`__exit__` method is invoked. If an exception
2007-08-15 11:28:22 -03:00
caused the suite to be exited, its type, value, and traceback are passed as
arguments to :meth:`__exit__`. Otherwise, three :const:`None` arguments are
supplied.
If the suite was exited due to an exception, and the return value from the
:meth:`__exit__` method was false, the exception is reraised. If the return
2007-08-15 11:28:22 -03:00
value was true, the exception is suppressed, and execution continues with the
statement following the :keyword:`with` statement.
If the suite was exited for any reason other than an exception, the return
value from :meth:`__exit__` is ignored, and execution proceeds at the normal
location for the kind of exit that was taken.
2007-08-15 11:28:22 -03:00
With more than one item, the context managers are processed as if multiple
:keyword:`with` statements were nested::
with A() as a, B() as b:
suite
is equivalent to ::
with A() as a:
with B() as b:
suite
.. versionchanged:: 3.1
Support for multiple context expressions.
2007-08-15 11:28:22 -03:00
.. seealso::
:pep:`0343` - The "with" statement
The specification, background, and examples for the Python :keyword:`with`
statement.
.. _function:
.. _def:
2007-08-15 11:28:22 -03:00
Function definitions
====================
.. index::
statement: def
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
pair: function; definition
pair: function; name
pair: name; binding
2007-08-15 11:28:22 -03:00
object: user-defined function
object: function
pair: function; name
pair: name; binding
2007-08-15 11:28:22 -03:00
A function definition defines a user-defined function object (see section
:ref:`types`):
.. productionlist::
2008-09-21 04:40:25 -03:00
funcdef: [`decorators`] "def" `funcname` "(" [`parameter_list`] ")" ["->" `expression`] ":" `suite`
2007-08-15 11:28:22 -03:00
decorators: `decorator`+
2011-12-23 22:01:43 -04:00
decorator: "@" `dotted_name` ["(" [`parameter_list` [","]] ")"] NEWLINE
2007-08-15 11:28:22 -03:00
dotted_name: `identifier` ("." `identifier`)*
parameter_list: (`defparameter` ",")*
: ( "*" [`parameter`] ("," `defparameter`)*
: [, "**" `parameter`]
: | "**" `parameter`
: | `defparameter` [","] )
parameter: `identifier` [":" `expression`]
defparameter: `parameter` ["=" `expression`]
funcname: `identifier`
A function definition is an executable statement. Its execution binds the
function name in the current local namespace to a function object (a wrapper
around the executable code for the function). This function object contains a
reference to the current global namespace as the global namespace to be used
when the function is called.
The function definition does not execute the function body; this gets executed
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
only when the function is called. [#]_
2007-08-15 11:28:22 -03:00
Merged revisions 62350-62355,62358-62359,62364-62365,62370,62372-62375,62378-62379,62381 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62350 | nick.coghlan | 2008-04-15 12:25:31 +0200 (Tue, 15 Apr 2008) | 1 line Issue 2439: add pkgutils.get_data() as a convenience wrapper for the PEP 302 get_data() API (contributed by Paul Moore) ........ r62351 | nick.coghlan | 2008-04-15 12:28:14 +0200 (Tue, 15 Apr 2008) | 1 line Add test file missing from rev 62350 ........ r62352 | benjamin.peterson | 2008-04-15 13:58:46 +0200 (Tue, 15 Apr 2008) | 2 lines Add myself to Doc/ACKS.txt ........ r62353 | andrew.kuchling | 2008-04-15 15:10:07 +0200 (Tue, 15 Apr 2008) | 6 lines Add *,**,@ to index, as suggested by http://farmdev.com/thoughts/24/what-does-the-def-star-variable-or-def-asterisk-parameter-syntax-do-in-python-/ The right entry type to use isn't clear; operator seems wrong, because *,**,@ aren't being used in expressions here. I put them as 'statement'; 'syntax' might be better. ........ r62354 | andrew.kuchling | 2008-04-15 15:10:41 +0200 (Tue, 15 Apr 2008) | 1 line Typo fix ........ r62355 | mark.dickinson | 2008-04-15 22:51:18 +0200 (Tue, 15 Apr 2008) | 3 lines Fix for possible signed overflow: the behaviour of -LONG_MIN is undefined in ANSI C. ........ r62358 | jeroen.ruigrok | 2008-04-16 14:47:01 +0200 (Wed, 16 Apr 2008) | 2 lines Reformat to 80 columns prior to adding documentation. ........ r62359 | jeroen.ruigrok | 2008-04-16 14:57:43 +0200 (Wed, 16 Apr 2008) | 2 lines Add details about the return value for mmap.flush(). ........ r62364 | raymond.hettinger | 2008-04-17 12:48:31 +0200 (Thu, 17 Apr 2008) | 1 line Issue 2648: Add leading zero to money format recipe in the docs. ........ r62365 | jeroen.ruigrok | 2008-04-17 14:39:45 +0200 (Thu, 17 Apr 2008) | 2 lines Be consistent in the use of read-only. ........ r62370 | andrew.kuchling | 2008-04-17 22:44:06 +0200 (Thu, 17 Apr 2008) | 1 line Typo fixes ........ r62372 | andrew.kuchling | 2008-04-18 04:40:47 +0200 (Fri, 18 Apr 2008) | 1 line Use correct parameter name ........ r62373 | andrew.kuchling | 2008-04-18 18:53:09 +0200 (Fri, 18 Apr 2008) | 1 line #2654: fix typo ........ r62374 | andrew.kuchling | 2008-04-18 20:28:23 +0200 (Fri, 18 Apr 2008) | 4 lines Remove personal note from Jim Roskind; it no longer applies, and the e-mail address is for a previous employer. Can we move the big long copyright statement into a sidebar or something? ........ r62375 | andrew.kuchling | 2008-04-18 20:39:55 +0200 (Fri, 18 Apr 2008) | 1 line Rewrite introductory section, and remove old section. (It was already commented-out, but why keep it?) ........ r62378 | skip.montanaro | 2008-04-18 22:35:46 +0200 (Fri, 18 Apr 2008) | 1 line resolve issue 2014 ........ r62379 | benjamin.peterson | 2008-04-18 22:45:33 +0200 (Fri, 18 Apr 2008) | 2 lines Fix indentation in sysmodule.c ........ r62381 | amaury.forgeotdarc | 2008-04-19 01:31:33 +0200 (Sat, 19 Apr 2008) | 3 lines Some tests did not pass on repeated calls (regrtest -R::) Perform additional cleanup, mostly deleting from sys.modules, or clearing the warnings registry. ........
2008-04-18 21:55:37 -03:00
.. index::
statement: @
Merged revisions 59259-59274 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59260 | lars.gustaebel | 2007-12-01 22:02:12 +0100 (Sat, 01 Dec 2007) | 5 lines Issue #1531: Read fileobj from the current offset, do not seek to the start. (will backport to 2.5) ........ r59262 | georg.brandl | 2007-12-01 23:24:47 +0100 (Sat, 01 Dec 2007) | 4 lines Document PyEval_* functions from ceval.c. Credits to Michael Sloan from GHOP. ........ r59263 | georg.brandl | 2007-12-01 23:27:56 +0100 (Sat, 01 Dec 2007) | 2 lines Add a few refcount data entries. ........ r59264 | georg.brandl | 2007-12-01 23:38:48 +0100 (Sat, 01 Dec 2007) | 4 lines Add test suite for cmd module. Written by Michael Schneider for GHOP. ........ r59265 | georg.brandl | 2007-12-01 23:42:46 +0100 (Sat, 01 Dec 2007) | 3 lines Add examples to the ElementTree documentation. Written by h4wk.cz for GHOP. ........ r59266 | georg.brandl | 2007-12-02 00:12:45 +0100 (Sun, 02 Dec 2007) | 3 lines Add "Using Python on Windows" document, by Robert Lehmann. Written for GHOP. ........ r59271 | georg.brandl | 2007-12-02 15:34:34 +0100 (Sun, 02 Dec 2007) | 3 lines Add example to mmap docs. Written for GHOP by Rafal Rawicki. ........ r59272 | georg.brandl | 2007-12-02 15:37:29 +0100 (Sun, 02 Dec 2007) | 2 lines Convert bdb.rst line endings to Unix style. ........ r59274 | georg.brandl | 2007-12-02 15:58:50 +0100 (Sun, 02 Dec 2007) | 4 lines Add more entries to the glossary. Written by Jeff Wheeler for GHOP. ........
2007-12-02 11:22:16 -04:00
A function definition may be wrapped by one or more :term:`decorator` expressions.
2007-08-15 11:28:22 -03:00
Decorator expressions are evaluated when the function is defined, in the scope
that contains the function definition. The result must be a callable, which is
invoked with the function object as the only argument. The returned value is
bound to the function name instead of the function object. Multiple decorators
are applied in nested fashion. For example, the following code ::
2007-08-15 11:28:22 -03:00
@f1(arg)
@f2
def func(): pass
is equivalent to ::
2007-08-15 11:28:22 -03:00
def func(): pass
func = f1(arg)(f2(func))
.. index:: triple: default; parameter; value
When one or more parameters have the form *parameter* ``=`` *expression*, the
function is said to have "default parameter values." For a parameter with a
default value, the corresponding argument may be omitted from a call, in which
case the parameter's default value is substituted. If a parameter has a default
value, all following parameters up until the "``*``" must also have a default
value --- this is a syntactic restriction that is not expressed by the grammar.
2007-08-15 11:28:22 -03:00
**Default parameter values are evaluated when the function definition is
executed.** This means that the expression is evaluated once, when the function
2011-10-19 04:58:56 -03:00
is defined, and that the same "pre-computed" value is used for each call. This
2007-08-15 11:28:22 -03:00
is especially important to understand when a default parameter is a mutable
object, such as a list or a dictionary: if the function modifies the object
(e.g. by appending an item to a list), the default value is in effect modified.
This is generally not what was intended. A way around this is to use ``None``
2007-08-15 11:28:22 -03:00
as the default, and explicitly test for it in the body of the function, e.g.::
def whats_on_the_telly(penguin=None):
if penguin is None:
penguin = []
penguin.append("property of the zoo")
return penguin
Merged revisions 62350-62355,62358-62359,62364-62365,62370,62372-62375,62378-62379,62381 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62350 | nick.coghlan | 2008-04-15 12:25:31 +0200 (Tue, 15 Apr 2008) | 1 line Issue 2439: add pkgutils.get_data() as a convenience wrapper for the PEP 302 get_data() API (contributed by Paul Moore) ........ r62351 | nick.coghlan | 2008-04-15 12:28:14 +0200 (Tue, 15 Apr 2008) | 1 line Add test file missing from rev 62350 ........ r62352 | benjamin.peterson | 2008-04-15 13:58:46 +0200 (Tue, 15 Apr 2008) | 2 lines Add myself to Doc/ACKS.txt ........ r62353 | andrew.kuchling | 2008-04-15 15:10:07 +0200 (Tue, 15 Apr 2008) | 6 lines Add *,**,@ to index, as suggested by http://farmdev.com/thoughts/24/what-does-the-def-star-variable-or-def-asterisk-parameter-syntax-do-in-python-/ The right entry type to use isn't clear; operator seems wrong, because *,**,@ aren't being used in expressions here. I put them as 'statement'; 'syntax' might be better. ........ r62354 | andrew.kuchling | 2008-04-15 15:10:41 +0200 (Tue, 15 Apr 2008) | 1 line Typo fix ........ r62355 | mark.dickinson | 2008-04-15 22:51:18 +0200 (Tue, 15 Apr 2008) | 3 lines Fix for possible signed overflow: the behaviour of -LONG_MIN is undefined in ANSI C. ........ r62358 | jeroen.ruigrok | 2008-04-16 14:47:01 +0200 (Wed, 16 Apr 2008) | 2 lines Reformat to 80 columns prior to adding documentation. ........ r62359 | jeroen.ruigrok | 2008-04-16 14:57:43 +0200 (Wed, 16 Apr 2008) | 2 lines Add details about the return value for mmap.flush(). ........ r62364 | raymond.hettinger | 2008-04-17 12:48:31 +0200 (Thu, 17 Apr 2008) | 1 line Issue 2648: Add leading zero to money format recipe in the docs. ........ r62365 | jeroen.ruigrok | 2008-04-17 14:39:45 +0200 (Thu, 17 Apr 2008) | 2 lines Be consistent in the use of read-only. ........ r62370 | andrew.kuchling | 2008-04-17 22:44:06 +0200 (Thu, 17 Apr 2008) | 1 line Typo fixes ........ r62372 | andrew.kuchling | 2008-04-18 04:40:47 +0200 (Fri, 18 Apr 2008) | 1 line Use correct parameter name ........ r62373 | andrew.kuchling | 2008-04-18 18:53:09 +0200 (Fri, 18 Apr 2008) | 1 line #2654: fix typo ........ r62374 | andrew.kuchling | 2008-04-18 20:28:23 +0200 (Fri, 18 Apr 2008) | 4 lines Remove personal note from Jim Roskind; it no longer applies, and the e-mail address is for a previous employer. Can we move the big long copyright statement into a sidebar or something? ........ r62375 | andrew.kuchling | 2008-04-18 20:39:55 +0200 (Fri, 18 Apr 2008) | 1 line Rewrite introductory section, and remove old section. (It was already commented-out, but why keep it?) ........ r62378 | skip.montanaro | 2008-04-18 22:35:46 +0200 (Fri, 18 Apr 2008) | 1 line resolve issue 2014 ........ r62379 | benjamin.peterson | 2008-04-18 22:45:33 +0200 (Fri, 18 Apr 2008) | 2 lines Fix indentation in sysmodule.c ........ r62381 | amaury.forgeotdarc | 2008-04-19 01:31:33 +0200 (Sat, 19 Apr 2008) | 3 lines Some tests did not pass on repeated calls (regrtest -R::) Perform additional cleanup, mostly deleting from sys.modules, or clearing the warnings registry. ........
2008-04-18 21:55:37 -03:00
.. index::
statement: *
statement: **
Function call semantics are described in more detail in section :ref:`calls`. A
2007-08-15 11:28:22 -03:00
function call always assigns values to all parameters mentioned in the parameter
list, either from position arguments, from keyword arguments, or from default
values. If the form "``*identifier``" is present, it is initialized to a tuple
receiving any excess positional parameters, defaulting to the empty tuple. If
the form "``**identifier``" is present, it is initialized to a new dictionary
receiving any excess keyword arguments, defaulting to a new empty dictionary.
Parameters after "``*``" or "``*identifier``" are keyword-only parameters and
may only be passed used keyword arguments.
.. index:: pair: function; annotations
Parameters may have annotations of the form "``: expression``" following the
parameter name. Any parameter may have an annotation even those of the form
``*identifier`` or ``**identifier``. Functions may have "return" annotation of
the form "``-> expression``" after the parameter list. These annotations can be
2007-08-15 11:28:22 -03:00
any valid Python expression and are evaluated when the function definition is
executed. Annotations may be evaluated in a different order than they appear in
the source code. The presence of annotations does not change the semantics of a
function. The annotation values are available as values of a dictionary keyed
2007-08-15 11:28:22 -03:00
by the parameters' names in the :attr:`__annotations__` attribute of the
function object.
.. index:: pair: lambda; form
It is also possible to create anonymous functions (functions not bound to a
name), for immediate use in expressions. This uses lambda forms, described in
section :ref:`lambda`. Note that the lambda form is merely a shorthand for a
simplified function definition; a function defined in a ":keyword:`def`"
statement can be passed around or assigned to another name just like a function
defined by a lambda form. The ":keyword:`def`" form is actually more powerful
since it allows the execution of multiple statements and annotations.
**Programmer's note:** Functions are first-class objects. A "``def``" form
executed inside a function definition defines a local function that can be
returned or passed around. Free variables used in the nested function can
access the local variables of the function containing the def. See section
:ref:`naming` for details.
.. seealso::
:pep:`3107` - Function Annotations
The original specification for function annotations.
2007-08-15 11:28:22 -03:00
.. _class:
Class definitions
=================
.. index::
object: class
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
statement: class
pair: class; definition
pair: class; name
pair: name; binding
pair: execution; frame
Merged revisions 59703-59773 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59704 | christian.heimes | 2008-01-04 04:15:05 +0100 (Fri, 04 Jan 2008) | 1 line Moved include "Python.h" in front of other imports to silence a warning. ........ r59706 | raymond.hettinger | 2008-01-04 04:22:53 +0100 (Fri, 04 Jan 2008) | 10 lines Minor fix-ups to named tuples: * Make the _replace() method respect subclassing. * Using property() to make _fields read-only wasn't a good idea. It caused len(Point._fields) to fail. * Add note to _cast() about length checking and alternative with the star-operator. ........ r59707 | jeffrey.yasskin | 2008-01-04 09:01:23 +0100 (Fri, 04 Jan 2008) | 3 lines Make math.{floor,ceil}({int,long}) return float again for backwards compatibility after r59671 made them return integral types. ........ r59709 | christian.heimes | 2008-01-04 14:21:07 +0100 (Fri, 04 Jan 2008) | 1 line Bug #1713: posixpath.ismount() claims symlink to a mountpoint is a mountpoint. ........ r59712 | lars.gustaebel | 2008-01-04 15:00:33 +0100 (Fri, 04 Jan 2008) | 5 lines Issue #1735: TarFile.extractall() now correctly sets directory permissions and times. (will backport to 2.5) ........ r59714 | andrew.kuchling | 2008-01-04 15:47:17 +0100 (Fri, 04 Jan 2008) | 1 line Update links to bug/patch tracker ........ r59716 | christian.heimes | 2008-01-04 16:23:30 +0100 (Fri, 04 Jan 2008) | 1 line Added interface to Windows' WSAIoctl and a simple example for a network sniffer. ........ r59717 | christian.heimes | 2008-01-04 16:29:00 +0100 (Fri, 04 Jan 2008) | 1 line And here is the rest of Hirokazu Yamamoto's patch for VS6.0 support. Thanks Hiro! ........ r59719 | christian.heimes | 2008-01-04 16:34:06 +0100 (Fri, 04 Jan 2008) | 1 line Reverted last transaction. It's the wrong branch. ........ r59721 | christian.heimes | 2008-01-04 16:48:06 +0100 (Fri, 04 Jan 2008) | 1 line socket.ioctl is only available on Windows ........ r59722 | andrew.kuchling | 2008-01-04 19:24:41 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59723 | andrew.kuchling | 2008-01-04 19:25:05 +0100 (Fri, 04 Jan 2008) | 1 line Fix markup ........ r59725 | guido.van.rossum | 2008-01-05 01:59:59 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1725 by Mark Dickinson, fixes incorrect conversion of -1e1000 and adds errors for -0x. ........ r59726 | guido.van.rossum | 2008-01-05 02:21:57 +0100 (Sat, 05 Jan 2008) | 2 lines Patch #1698 by Senthil: allow '@' in username when parsed by urlparse.py. ........ r59727 | raymond.hettinger | 2008-01-05 02:35:43 +0100 (Sat, 05 Jan 2008) | 1 line Improve namedtuple's _cast() method with a docstring, new name, and error-checking. ........ r59728 | raymond.hettinger | 2008-01-05 03:17:24 +0100 (Sat, 05 Jan 2008) | 1 line Add error-checking to namedtuple's _replace() method. ........ r59730 | fred.drake | 2008-01-05 05:38:38 +0100 (Sat, 05 Jan 2008) | 2 lines clean up a comment ........ r59731 | jeffrey.yasskin | 2008-01-05 09:47:13 +0100 (Sat, 05 Jan 2008) | 11 lines Continue rolling back pep-3141 changes that changed behavior from 2.5. This round included: * Revert round to its 2.6 behavior (half away from 0). * Because round, floor, and ceil always return float again, it's no longer necessary to have them delegate to __xxx___, so I've ripped that out of their implementations and the Real ABC. This also helps in implementing types that work in both 2.6 and 3.0: you return int from the __xxx__ methods, and let it get enabled by the version upgrade. * Make pow(-1, .5) raise a ValueError again. ........ r59736 | andrew.kuchling | 2008-01-05 16:13:49 +0100 (Sat, 05 Jan 2008) | 1 line Fix comment typo ........ r59738 | thomas.heller | 2008-01-05 18:15:44 +0100 (Sat, 05 Jan 2008) | 1 line Add myself. ........ r59739 | georg.brandl | 2008-01-05 18:49:17 +0100 (Sat, 05 Jan 2008) | 2 lines Fix C++-style comment. ........ r59742 | georg.brandl | 2008-01-05 20:28:16 +0100 (Sat, 05 Jan 2008) | 2 lines Remove with_statement future imports from 2.6 docs. ........ r59743 | georg.brandl | 2008-01-05 20:29:45 +0100 (Sat, 05 Jan 2008) | 2 lines Simplify index entries; fix #1712. ........ r59744 | georg.brandl | 2008-01-05 20:44:22 +0100 (Sat, 05 Jan 2008) | 2 lines Doc patch #1730 from Robin Stocker; minor corrections mostly to os.rst. ........ r59749 | georg.brandl | 2008-01-05 21:29:13 +0100 (Sat, 05 Jan 2008) | 2 lines Revert socket.rst to unix-eol. ........ r59750 | georg.brandl | 2008-01-05 21:33:46 +0100 (Sat, 05 Jan 2008) | 2 lines Set native svn:eol-style property for text files. ........ r59752 | georg.brandl | 2008-01-05 21:46:29 +0100 (Sat, 05 Jan 2008) | 2 lines #1719: capitalization error in "UuidCreate". ........ r59753 | georg.brandl | 2008-01-05 22:02:25 +0100 (Sat, 05 Jan 2008) | 2 lines Repair markup. ........ r59754 | georg.brandl | 2008-01-05 22:10:50 +0100 (Sat, 05 Jan 2008) | 2 lines Use markup. ........ r59757 | christian.heimes | 2008-01-05 22:35:52 +0100 (Sat, 05 Jan 2008) | 1 line Final adjustments for #1601 ........ r59758 | guido.van.rossum | 2008-01-05 23:19:06 +0100 (Sat, 05 Jan 2008) | 3 lines Patch #1637: fix urlparse for URLs like 'http://x.com?arg=/foo'. Fix by John Nagle. ........ r59759 | guido.van.rossum | 2008-01-05 23:20:01 +0100 (Sat, 05 Jan 2008) | 2 lines Add John Nagle (of issue #1637). ........ r59765 | raymond.hettinger | 2008-01-06 10:02:24 +0100 (Sun, 06 Jan 2008) | 1 line Small code simplification. Forgot that classmethods can be called from intances. ........ r59766 | martin.v.loewis | 2008-01-06 11:09:48 +0100 (Sun, 06 Jan 2008) | 2 lines Use vcbuild for VS 2009. ........ r59767 | martin.v.loewis | 2008-01-06 12:03:43 +0100 (Sun, 06 Jan 2008) | 2 lines Package using VS 2008. ........ r59768 | martin.v.loewis | 2008-01-06 12:13:16 +0100 (Sun, 06 Jan 2008) | 2 lines Don't try to package msvcr90 for the moment. ........ r59769 | georg.brandl | 2008-01-06 15:17:36 +0100 (Sun, 06 Jan 2008) | 4 lines #1696393: don't check for '.' and '..' in ntpath.walk since they aren't returned from os.listdir anymore. Reported by Michael Haggerty. ........ r59770 | georg.brandl | 2008-01-06 15:27:15 +0100 (Sun, 06 Jan 2008) | 3 lines #1742: don't raise exception on os.path.relpath("a", "a"), but return os.curdir. Reported by Jesse Towner. ........ r59771 | georg.brandl | 2008-01-06 15:33:52 +0100 (Sun, 06 Jan 2008) | 2 lines #1591: Clarify docstring of Popen3. ........ r59772 | georg.brandl | 2008-01-06 16:30:34 +0100 (Sun, 06 Jan 2008) | 2 lines #1680: fix context manager example function name. ........ r59773 | georg.brandl | 2008-01-06 16:34:57 +0100 (Sun, 06 Jan 2008) | 2 lines #1755097: document default values for [].sort() and sorted(). ........
2008-01-06 12:59:19 -04:00
single: inheritance
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
single: docstring
2007-08-15 11:28:22 -03:00
A class definition defines a class object (see section :ref:`types`):
.. productionlist::
classdef: [`decorators`] "class" `classname` [`inheritance`] ":" `suite`
inheritance: "(" [`parameter_list`] ")"
2007-08-15 11:28:22 -03:00
classname: `identifier`
A class definition is an executable statement. The inheritance list usually
gives a list of base classes (see :ref:`metaclasses` for more advanced uses), so
each item in the list should evaluate to a class object which allows
subclassing. Classes without an inheritance list inherit, by default, from the
base class :class:`object`; hence, ::
class Foo:
pass
is equivalent to ::
class Foo(object):
pass
The class's suite is then executed in a new execution frame (see :ref:`naming`),
using a newly created local namespace and the original global namespace.
(Usually, the suite contains mostly function definitions.) When the class's
suite finishes execution, its execution frame is discarded but its local
namespace is saved. [#]_ A class object is then created using the inheritance
list for the base classes and the saved local namespace for the attribute
dictionary. The class name is bound to this class object in the original local
namespace.
Class creation can be customized heavily using :ref:`metaclasses <metaclasses>`.
2007-08-15 11:28:22 -03:00
Classes can also be decorated: just like when decorating functions, ::
@f1(arg)
@f2
class Foo: pass
is equivalent to ::
class Foo: pass
Foo = f1(arg)(f2(Foo))
The evaluation rules for the decorator expressions are the same as for function
decorators. The result must be a class object, which is then bound to the class
name.
2007-08-15 11:28:22 -03:00
**Programmer's note:** Variables defined in the class definition are class
attributes; they are shared by instances. Instance attributes can be set in a
method with ``self.name = value``. Both class and instance attributes are
accessible through the notation "``self.name``", and an instance attribute hides
a class attribute with the same name when accessed in this way. Class
attributes can be used as defaults for instance attributes, but using mutable
values there can lead to unexpected results. :ref:`Descriptors <descriptors>`
can be used to create instance variables with different implementation details.
2007-08-15 11:28:22 -03:00
.. seealso::
2011-03-11 14:50:42 -04:00
:pep:`3115` - Metaclasses in Python 3
:pep:`3129` - Class Decorators
2007-08-15 11:28:22 -03:00
.. rubric:: Footnotes
.. [#] The exception is propagated to the invocation stack unless
there is a :keyword:`finally` clause which happens to raise another
exception. That new exception causes the old one to be lost.
2007-08-15 11:28:22 -03:00
2009-10-22 13:08:10 -03:00
.. [#] Currently, control "flows off the end" except in the case of an exception
or the execution of a :keyword:`return`, :keyword:`continue`, or
:keyword:`break` statement.
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
.. [#] A string literal appearing as the first statement in the function body is
transformed into the function's ``__doc__`` attribute and therefore the
function's :term:`docstring`.
.. [#] A string literal appearing as the first statement in the class body is
transformed into the namespace's ``__doc__`` item and therefore the class's
:term:`docstring`.