cpython/Doc/library/warnings.rst

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:mod:`warnings` --- Warning control
===================================
.. module:: warnings
:synopsis: Issue warning messages and control their disposition.
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**Source code:** :source:`Lib/warnings.py`
.. index:: single: warnings
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--------------
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Warning messages are typically issued in situations where it is useful to alert
the user of some condition in a program, where that condition (normally) doesn't
warrant raising an exception and terminating the program. For example, one
might want to issue a warning when a program uses an obsolete module.
Python programmers issue warnings by calling the :func:`warn` function defined
in this module. (C programmers use :c:func:`PyErr_WarnEx`; see
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:ref:`exceptionhandling` for details).
Warning messages are normally written to :data:`sys.stderr`, but their disposition
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can be changed flexibly, from ignoring all warnings to turning them into
exceptions. The disposition of warnings can vary based on the :ref:`warning category
<warning-categories>`, the text of the warning message, and the source location where it
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is issued. Repetitions of a particular warning for the same source location are
typically suppressed.
There are two stages in warning control: first, each time a warning is issued, a
determination is made whether a message should be issued or not; next, if a
message is to be issued, it is formatted and printed using a user-settable hook.
The determination whether to issue a warning message is controlled by the
:ref:`warning filter <warning-filter>`, which is a sequence of matching rules and actions. Rules can be
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added to the filter by calling :func:`filterwarnings` and reset to its default
state by calling :func:`resetwarnings`.
The printing of warning messages is done by calling :func:`showwarning`, which
may be overridden; the default implementation of this function formats the
message by calling :func:`formatwarning`, which is also available for use by
custom implementations.
.. seealso::
:func:`logging.captureWarnings` allows you to handle all warnings with
the standard logging infrastructure.
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.. _warning-categories:
Warning Categories
------------------
There are a number of built-in exceptions that represent warning categories.
This categorization is useful to be able to filter out groups of warnings.
While these are technically
:ref:`built-in exceptions <warning-categories-as-exceptions>`, they are
documented here, because conceptually they belong to the warnings mechanism.
User code can define additional warning categories by subclassing one of the
standard warning categories. A warning category must always be a subclass of
the :exc:`Warning` class.
The following warnings category classes are currently defined:
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.. tabularcolumns:: |l|p{0.6\linewidth}|
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+----------------------------------+-----------------------------------------------+
| Class | Description |
+==================================+===============================================+
| :exc:`Warning` | This is the base class of all warning |
| | category classes. It is a subclass of |
| | :exc:`Exception`. |
+----------------------------------+-----------------------------------------------+
| :exc:`UserWarning` | The default category for :func:`warn`. |
+----------------------------------+-----------------------------------------------+
| :exc:`DeprecationWarning` | Base category for warnings about deprecated |
| | features when those warnings are intended for |
| | other Python developers (ignored by default, |
| | unless triggered by code in ``__main__``). |
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+----------------------------------+-----------------------------------------------+
| :exc:`SyntaxWarning` | Base category for warnings about dubious |
| | syntactic features. |
+----------------------------------+-----------------------------------------------+
| :exc:`RuntimeWarning` | Base category for warnings about dubious |
| | runtime features. |
+----------------------------------+-----------------------------------------------+
| :exc:`FutureWarning` | Base category for warnings about deprecated |
| | features when those warnings are intended for |
| | end users of applications that are written in |
| | Python. |
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+----------------------------------+-----------------------------------------------+
| :exc:`PendingDeprecationWarning` | Base category for warnings about features |
| | that will be deprecated in the future |
| | (ignored by default). |
+----------------------------------+-----------------------------------------------+
| :exc:`ImportWarning` | Base category for warnings triggered during |
| | the process of importing a module (ignored by |
| | default). |
+----------------------------------+-----------------------------------------------+
| :exc:`UnicodeWarning` | Base category for warnings related to |
| | Unicode. |
+----------------------------------+-----------------------------------------------+
| :exc:`BytesWarning` | Base category for warnings related to |
| | :class:`bytes` and :class:`bytearray`. |
+----------------------------------+-----------------------------------------------+
| :exc:`ResourceWarning` | Base category for warnings related to |
| | resource usage (ignored by default). |
+----------------------------------+-----------------------------------------------+
.. versionchanged:: 3.7
Previously :exc:`DeprecationWarning` and :exc:`FutureWarning` were
distinguished based on whether a feature was being removed entirely or
changing its behaviour. They are now distinguished based on their
intended audience and the way they're handled by the default warnings
filters.
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.. _warning-filter:
The Warnings Filter
-------------------
The warnings filter controls whether warnings are ignored, displayed, or turned
into errors (raising an exception).
Conceptually, the warnings filter maintains an ordered list of filter
specifications; any specific warning is matched against each filter
specification in the list in turn until a match is found; the filter determines
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the disposition of the match. Each entry is a tuple of the form (*action*,
*message*, *category*, *module*, *lineno*), where:
* *action* is one of the following strings:
+---------------+----------------------------------------------+
| Value | Disposition |
+===============+==============================================+
| ``"default"`` | print the first occurrence of matching |
| | warnings for each location (module + |
| | line number) where the warning is issued |
+---------------+----------------------------------------------+
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| ``"error"`` | turn matching warnings into exceptions |
+---------------+----------------------------------------------+
| ``"ignore"`` | never print matching warnings |
+---------------+----------------------------------------------+
| ``"always"`` | always print matching warnings |
+---------------+----------------------------------------------+
| ``"module"`` | print the first occurrence of matching |
| | warnings for each module where the warning |
| | is issued (regardless of line number) |
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+---------------+----------------------------------------------+
| ``"once"`` | print only the first occurrence of matching |
| | warnings, regardless of location |
+---------------+----------------------------------------------+
* *message* is a string containing a regular expression that the start of
the warning message must match. The expression is compiled to always be
case-insensitive.
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* *category* is a class (a subclass of :exc:`Warning`) of which the warning
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category must be a subclass in order to match.
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* *module* is a string containing a regular expression that the module name must
match. The expression is compiled to be case-sensitive.
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* *lineno* is an integer that the line number where the warning occurred must
Merged revisions 74277,74321,74323,74326,74355,74465,74467,74488,74492,74513,74531,74549,74553,74625,74632,74643-74644,74647,74652,74666,74671,74727,74739 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74277 | sean.reifschneider | 2009-08-01 18:54:55 -0500 (Sat, 01 Aug 2009) | 3 lines - Issue #6624: yArg_ParseTuple with "s" format when parsing argument with NUL: Bogus TypeError detail string. ........ r74321 | guilherme.polo | 2009-08-05 11:51:41 -0500 (Wed, 05 Aug 2009) | 1 line Easier reference to find (at least while svn continues being used). ........ r74323 | guilherme.polo | 2009-08-05 18:48:26 -0500 (Wed, 05 Aug 2009) | 1 line Typo. ........ r74326 | jesse.noller | 2009-08-05 21:05:56 -0500 (Wed, 05 Aug 2009) | 1 line Fix issue 4660: spurious task_done errors in multiprocessing, remove doc note for from_address ........ r74355 | gregory.p.smith | 2009-08-12 12:02:37 -0500 (Wed, 12 Aug 2009) | 2 lines comment typo fix ........ r74465 | vinay.sajip | 2009-08-15 18:23:12 -0500 (Sat, 15 Aug 2009) | 1 line Added section on logging to one file from multiple processes. ........ r74467 | vinay.sajip | 2009-08-15 18:34:47 -0500 (Sat, 15 Aug 2009) | 1 line Refined section on logging to one file from multiple processes. ........ r74488 | vinay.sajip | 2009-08-17 08:14:37 -0500 (Mon, 17 Aug 2009) | 1 line Further refined section on logging to one file from multiple processes. ........ r74492 | r.david.murray | 2009-08-17 14:26:49 -0500 (Mon, 17 Aug 2009) | 2 lines Issue 6685: 'toupper' -> 'upper' in cgi doc example explanation. ........ r74513 | skip.montanaro | 2009-08-18 09:37:52 -0500 (Tue, 18 Aug 2009) | 1 line missing module ref (issue6723) ........ r74531 | vinay.sajip | 2009-08-20 17:04:32 -0500 (Thu, 20 Aug 2009) | 1 line Added section on exceptions raised during logging. ........ r74549 | benjamin.peterson | 2009-08-24 12:42:36 -0500 (Mon, 24 Aug 2009) | 1 line fix pdf building by teaching latex the right encoding package ........ r74553 | r.david.murray | 2009-08-26 20:04:59 -0500 (Wed, 26 Aug 2009) | 2 lines Remove leftover text from end of sentence. ........ r74625 | benjamin.peterson | 2009-09-01 17:27:57 -0500 (Tue, 01 Sep 2009) | 1 line remove the check that classmethod's argument is a callable ........ r74632 | georg.brandl | 2009-09-03 02:27:26 -0500 (Thu, 03 Sep 2009) | 1 line #6828: fix wrongly highlighted blocks. ........ r74643 | georg.brandl | 2009-09-04 01:59:20 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #2666: Handle BROWSER environment variable properly for unknown browser names in the webbrowser module. ........ r74644 | georg.brandl | 2009-09-04 02:55:14 -0500 (Fri, 04 Sep 2009) | 1 line #5047: remove Monterey support from configure. ........ r74647 | georg.brandl | 2009-09-04 03:17:04 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #5275: In Cookie's Cookie.load(), properly handle non-string arguments as documented. ........ r74652 | georg.brandl | 2009-09-04 06:25:37 -0500 (Fri, 04 Sep 2009) | 1 line #6756: add some info about the "acct" parameter. ........ r74666 | georg.brandl | 2009-09-05 04:04:09 -0500 (Sat, 05 Sep 2009) | 1 line #6841: remove duplicated word. ........ r74671 | georg.brandl | 2009-09-05 11:47:17 -0500 (Sat, 05 Sep 2009) | 1 line #6843: add link from filterwarnings to where the meaning of the arguments is covered. ........ r74727 | benjamin.peterson | 2009-09-08 18:04:22 -0500 (Tue, 08 Sep 2009) | 1 line #6865 fix ref counting in initialization of pwd module ........ r74739 | georg.brandl | 2009-09-11 02:55:20 -0500 (Fri, 11 Sep 2009) | 1 line Move function back to its section. ........
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match, or ``0`` to match all line numbers.
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Since the :exc:`Warning` class is derived from the built-in :exc:`Exception`
class, to turn a warning into an error we simply raise ``category(message)``.
If a warning is reported and doesn't match any registered filter then the
"default" action is applied (hence its name).
.. _describing-warning-filters:
Describing Warning Filters
~~~~~~~~~~~~~~~~~~~~~~~~~~
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The warnings filter is initialized by :option:`-W` options passed to the Python
interpreter command line and the :envvar:`PYTHONWARNINGS` environment variable.
The interpreter saves the arguments for all supplied entries without
interpretation in :data:`sys.warnoptions`; the :mod:`warnings` module parses these
when it is first imported (invalid options are ignored, after printing a
message to :data:`sys.stderr`).
Individual warnings filters are specified as a sequence of fields separated by
colons::
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action:message:category:module:line
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The meaning of each of these fields is as described in :ref:`warning-filter`.
When listing multiple filters on a single line (as for
:envvar:`PYTHONWARNINGS`), the individual filters are separated by commas and
the filters listed later take precedence over those listed before them (as
they're applied left-to-right, and the most recently applied filters take
precedence over earlier ones).
Commonly used warning filters apply to either all warnings, warnings in a
particular category, or warnings raised by particular modules or packages.
Some examples::
default # Show all warnings (even those ignored by default)
ignore # Ignore all warnings
error # Convert all warnings to errors
error::ResourceWarning # Treat ResourceWarning messages as errors
default::DeprecationWarning # Show DeprecationWarning messages
ignore,default:::mymodule # Only report warnings triggered by "mymodule"
error:::mymodule[.*] # Convert warnings to errors in "mymodule"
# and any subpackages of "mymodule"
.. _default-warning-filter:
Default Warning Filter
~~~~~~~~~~~~~~~~~~~~~~
By default, Python installs several warning filters, which can be overridden by
the :option:`-W` command-line option, the :envvar:`PYTHONWARNINGS` environment
variable and calls to :func:`filterwarnings`.
In regular release builds, the default warning filter has the following entries
(in order of precedence)::
default::DeprecationWarning:__main__
ignore::DeprecationWarning
ignore::PendingDeprecationWarning
ignore::ImportWarning
ignore::ResourceWarning
In a :ref:`debug build <debug-build>`, the list of default warning filters is empty.
.. versionchanged:: 3.2
:exc:`DeprecationWarning` is now ignored by default in addition to
:exc:`PendingDeprecationWarning`.
.. versionchanged:: 3.7
:exc:`DeprecationWarning` is once again shown by default when triggered
directly by code in ``__main__``.
.. versionchanged:: 3.7
:exc:`BytesWarning` no longer appears in the default filter list and is
instead configured via :data:`sys.warnoptions` when :option:`-b` is specified
twice.
.. _warning-disable:
Overriding the default filter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Developers of applications written in Python may wish to hide *all* Python level
warnings from their users by default, and only display them when running tests
or otherwise working on the application. The :data:`sys.warnoptions` attribute
used to pass filter configurations to the interpreter can be used as a marker to
indicate whether or not warnings should be disabled::
import sys
if not sys.warnoptions:
import warnings
warnings.simplefilter("ignore")
Developers of test runners for Python code are advised to instead ensure that
*all* warnings are displayed by default for the code under test, using code
like::
import sys
if not sys.warnoptions:
import os, warnings
warnings.simplefilter("default") # Change the filter in this process
os.environ["PYTHONWARNINGS"] = "default" # Also affect subprocesses
Finally, developers of interactive shells that run user code in a namespace
other than ``__main__`` are advised to ensure that :exc:`DeprecationWarning`
messages are made visible by default, using code like the following (where
``user_ns`` is the module used to execute code entered interactively)::
import warnings
warnings.filterwarnings("default", category=DeprecationWarning,
module=user_ns.get("__name__"))
.. _warning-suppress:
Temporarily Suppressing Warnings
--------------------------------
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If you are using code that you know will raise a warning, such as a deprecated
function, but do not want to see the warning (even when warnings have been
explicitly configured via the command line), then it is possible to suppress
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the warning using the :class:`catch_warnings` context manager::
import warnings
def fxn():
warnings.warn("deprecated", DeprecationWarning)
with warnings.catch_warnings():
warnings.simplefilter("ignore")
fxn()
While within the context manager all warnings will simply be ignored. This
allows you to use known-deprecated code without having to see the warning while
not suppressing the warning for other code that might not be aware of its use
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2010-04-11 13:12:57 -03:00
of deprecated code. Note: this can only be guaranteed in a single-threaded
application. If two or more threads use the :class:`catch_warnings` context
manager at the same time, the behavior is undefined.
.. _warning-testing:
Testing Warnings
----------------
To test warnings raised by code, use the :class:`catch_warnings` context
manager. With it you can temporarily mutate the warnings filter to facilitate
your testing. For instance, do the following to capture all raised warnings to
check::
import warnings
def fxn():
warnings.warn("deprecated", DeprecationWarning)
with warnings.catch_warnings(record=True) as w:
# Cause all warnings to always be triggered.
warnings.simplefilter("always")
# Trigger a warning.
fxn()
# Verify some things
assert len(w) == 1
Merged revisions 74074,74077,74111,74188,74192-74193,74200,74252-74253,74258-74261 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74074 | georg.brandl | 2009-07-18 05:03:10 -0400 (Sat, 18 Jul 2009) | 1 line #6513: fix example code: warning categories are classes, not instances. ........ r74077 | georg.brandl | 2009-07-18 05:43:40 -0400 (Sat, 18 Jul 2009) | 1 line #6489: fix an ambiguity in getiterator() documentation. ........ r74111 | benjamin.peterson | 2009-07-20 09:30:10 -0400 (Mon, 20 Jul 2009) | 1 line remove docs for deprecated -p option ........ r74188 | benjamin.peterson | 2009-07-23 10:25:31 -0400 (Thu, 23 Jul 2009) | 1 line use bools ........ r74192 | georg.brandl | 2009-07-24 12:28:38 -0400 (Fri, 24 Jul 2009) | 1 line Fix arg types of et#. ........ r74193 | georg.brandl | 2009-07-24 12:46:38 -0400 (Fri, 24 Jul 2009) | 1 line Dont put "void" in signature for nullary functions. ........ r74200 | georg.brandl | 2009-07-25 09:02:15 -0400 (Sat, 25 Jul 2009) | 1 line #6571: add index entries for more operators. ........ r74252 | georg.brandl | 2009-07-29 12:06:31 -0400 (Wed, 29 Jul 2009) | 1 line #6593: fix link targets. ........ r74253 | georg.brandl | 2009-07-29 12:09:17 -0400 (Wed, 29 Jul 2009) | 1 line #6591: add reference to ioctl in fcntl module for platforms other than Windows. ........ r74258 | georg.brandl | 2009-07-29 12:57:05 -0400 (Wed, 29 Jul 2009) | 1 line Add a link to readline, and mention IPython and bpython. ........ r74259 | georg.brandl | 2009-07-29 13:07:21 -0400 (Wed, 29 Jul 2009) | 1 line Fix some markup and small factual glitches found by M. Markert. ........ r74260 | georg.brandl | 2009-07-29 13:15:20 -0400 (Wed, 29 Jul 2009) | 1 line Fix a few markup glitches. ........ r74261 | georg.brandl | 2009-07-29 13:50:25 -0400 (Wed, 29 Jul 2009) | 1 line Rewrite the section about classes a bit; mostly tidbits, and a larger update to the section about "private" variables to reflect the Pythonic consensus better. ........
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assert issubclass(w[-1].category, DeprecationWarning)
assert "deprecated" in str(w[-1].message)
One can also cause all warnings to be exceptions by using ``error`` instead of
``always``. One thing to be aware of is that if a warning has already been
raised because of a ``once``/``default`` rule, then no matter what filters are
set the warning will not be seen again unless the warnings registry related to
the warning has been cleared.
Once the context manager exits, the warnings filter is restored to its state
when the context was entered. This prevents tests from changing the warnings
filter in unexpected ways between tests and leading to indeterminate test
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results. The :func:`showwarning` function in the module is also restored to
Merged revisions 79307,79408,79430,79533,79542,79579-79580,79585-79587,79607-79608,79622,79717,79820,79822,79828,79862,79875,79923-79924,79941-79943,79945,79947,79951-79952 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r79307 | florent.xicluna | 2010-03-22 17:45:50 -0500 (Mon, 22 Mar 2010) | 2 lines #7667: Fix doctest failures with non-ASCII paths. ........ r79408 | victor.stinner | 2010-03-24 20:18:38 -0500 (Wed, 24 Mar 2010) | 2 lines Fix a gcc warning introduced by r79397. ........ r79430 | brian.curtin | 2010-03-25 18:48:54 -0500 (Thu, 25 Mar 2010) | 2 lines Fix #6538. Markup RegexObject and MatchObject as classes. Patch by Ryan Arana. ........ r79533 | barry.warsaw | 2010-03-31 16:07:16 -0500 (Wed, 31 Mar 2010) | 6 lines - Issue #8233: When run as a script, py_compile.py optionally takes a single argument `-` which tells it to read files to compile from stdin. Each line is read on demand and the named file is compiled immediately. (Original patch by Piotr O?\197?\188arowski). ........ r79542 | r.david.murray | 2010-03-31 20:28:39 -0500 (Wed, 31 Mar 2010) | 3 lines A couple small grammar fixes in test.rst, and rewrite the check_warnings docs to be clearer. ........ r79579 | georg.brandl | 2010-04-02 03:34:41 -0500 (Fri, 02 Apr 2010) | 1 line Add 2.6.5. ........ r79580 | georg.brandl | 2010-04-02 03:39:09 -0500 (Fri, 02 Apr 2010) | 1 line #2768: add a note on how to get a file descriptor. ........ r79585 | georg.brandl | 2010-04-02 04:03:18 -0500 (Fri, 02 Apr 2010) | 1 line Remove col-spanning cells in logging docs. ........ r79586 | georg.brandl | 2010-04-02 04:07:42 -0500 (Fri, 02 Apr 2010) | 1 line Document PyImport_ExecCodeModuleEx(). ........ r79587 | georg.brandl | 2010-04-02 04:11:49 -0500 (Fri, 02 Apr 2010) | 1 line #8012: clarification in generator glossary entry. ........ r79607 | andrew.kuchling | 2010-04-02 12:48:23 -0500 (Fri, 02 Apr 2010) | 1 line #6647: document that catch_warnings is not thread-safe ........ r79608 | andrew.kuchling | 2010-04-02 12:54:26 -0500 (Fri, 02 Apr 2010) | 1 line #6647: add note to two examples ........ r79622 | tarek.ziade | 2010-04-02 16:34:19 -0500 (Fri, 02 Apr 2010) | 1 line removed documentation on code that was reverted and pushed into distutils2 ........ r79717 | antoine.pitrou | 2010-04-03 16:22:38 -0500 (Sat, 03 Apr 2010) | 4 lines Fix wording / typography, and a slightly misleading statement (memoryviews don't support complex structures right now) ........ r79820 | benjamin.peterson | 2010-04-05 22:34:09 -0500 (Mon, 05 Apr 2010) | 1 line ready _sre types ........ r79822 | georg.brandl | 2010-04-06 03:18:15 -0500 (Tue, 06 Apr 2010) | 1 line #8320: document return value of recv_into(). ........ r79828 | georg.brandl | 2010-04-06 09:33:44 -0500 (Tue, 06 Apr 2010) | 1 line Add JP. ........ r79862 | georg.brandl | 2010-04-06 15:27:59 -0500 (Tue, 06 Apr 2010) | 1 line Fix syntax. ........ r79875 | mark.dickinson | 2010-04-06 17:18:23 -0500 (Tue, 06 Apr 2010) | 1 line More NaN consistency doc fixes. ........ r79923 | georg.brandl | 2010-04-10 06:15:24 -0500 (Sat, 10 Apr 2010) | 1 line #8360: skipTest was added in 2.7. ........ r79924 | georg.brandl | 2010-04-10 06:16:59 -0500 (Sat, 10 Apr 2010) | 1 line #8346: update version. ........ r79941 | andrew.kuchling | 2010-04-10 20:39:36 -0500 (Sat, 10 Apr 2010) | 1 line Two grammar fixes ........ r79942 | andrew.kuchling | 2010-04-10 20:40:06 -0500 (Sat, 10 Apr 2010) | 1 line Punctuation fix ........ r79943 | andrew.kuchling | 2010-04-10 20:40:30 -0500 (Sat, 10 Apr 2010) | 1 line Add various items ........ r79945 | andrew.kuchling | 2010-04-10 20:40:49 -0500 (Sat, 10 Apr 2010) | 1 line name correct ........ r79947 | andrew.kuchling | 2010-04-10 20:44:13 -0500 (Sat, 10 Apr 2010) | 1 line Remove distutils section ........ r79951 | andrew.kuchling | 2010-04-11 07:48:08 -0500 (Sun, 11 Apr 2010) | 1 line Two typo fixes ........ r79952 | andrew.kuchling | 2010-04-11 07:49:37 -0500 (Sun, 11 Apr 2010) | 1 line Add two items ........
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its original value. Note: this can only be guaranteed in a single-threaded
application. If two or more threads use the :class:`catch_warnings` context
manager at the same time, the behavior is undefined.
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When testing multiple operations that raise the same kind of warning, it
is important to test them in a manner that confirms each operation is raising
a new warning (e.g. set warnings to be raised as exceptions and check the
operations raise exceptions, check that the length of the warning list
continues to increase after each operation, or else delete the previous
entries from the warnings list before each new operation).
.. _warning-ignored:
Updating Code For New Versions of Dependencies
----------------------------------------------
Warning categories that are primarily of interest to Python developers (rather
than end users of applications written in Python) are ignored by default.
Notably, this "ignored by default" list includes :exc:`DeprecationWarning`
(for every module except ``__main__``), which means developers should make sure
to test their code with typically ignored warnings made visible in order to
receive timely notifications of future breaking API changes (whether in the
standard library or third party packages).
In the ideal case, the code will have a suitable test suite, and the test runner
will take care of implicitly enabling all warnings when running tests
(the test runner provided by the :mod:`unittest` module does this).
In less ideal cases, applications can be checked for use of deprecated
interfaces by passing :option:`-Wd <-W>` to the Python interpreter (this is
shorthand for :option:`!-W default`) or setting ``PYTHONWARNINGS=default`` in
the environment. This enables default handling for all warnings, including those
that are ignored by default. To change what action is taken for encountered
warnings you can change what argument is passed to :option:`-W` (e.g.
:option:`!-W error`). See the :option:`-W` flag for more details on what is
possible.
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.. _warning-functions:
Available Functions
-------------------
.. function:: warn(message, category=None, stacklevel=1, source=None)
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Issue a warning, or maybe ignore it or raise an exception. The *category*
argument, if given, must be a :ref:`warning category class <warning-categories>`; it
defaults to :exc:`UserWarning`. Alternatively, *message* can be a :exc:`Warning` instance,
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in which case *category* will be ignored and ``message.__class__`` will be used.
In this case, the message text will be ``str(message)``. This function raises an
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exception if the particular warning issued is changed into an error by the
:ref:`warnings filter <warning-filter>`. The *stacklevel* argument can be used by wrapper
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functions written in Python, like this::
def deprecation(message):
warnings.warn(message, DeprecationWarning, stacklevel=2)
This makes the warning refer to :func:`deprecation`'s caller, rather than to the
source of :func:`deprecation` itself (since the latter would defeat the purpose
of the warning message).
*source*, if supplied, is the destroyed object which emitted a
:exc:`ResourceWarning`.
.. versionchanged:: 3.6
Added *source* parameter.
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.. function:: warn_explicit(message, category, filename, lineno, module=None, registry=None, module_globals=None, source=None)
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This is a low-level interface to the functionality of :func:`warn`, passing in
explicitly the message, category, filename and line number, and optionally the
module name and the registry (which should be the ``__warningregistry__``
dictionary of the module). The module name defaults to the filename with
``.py`` stripped; if no registry is passed, the warning is never suppressed.
*message* must be a string and *category* a subclass of :exc:`Warning` or
*message* may be a :exc:`Warning` instance, in which case *category* will be
ignored.
*module_globals*, if supplied, should be the global namespace in use by the code
for which the warning is issued. (This argument is used to support displaying
source for modules found in zipfiles or other non-filesystem import
sources).
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*source*, if supplied, is the destroyed object which emitted a
:exc:`ResourceWarning`.
.. versionchanged:: 3.6
Add the *source* parameter.
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.. function:: showwarning(message, category, filename, lineno, file=None, line=None)
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Write a warning to a file. The default implementation calls
Merged revisions 62260-62261,62266,62271,62277-62279,62289-62290,62293-62298,62302-62306,62308,62311,62313-62315,62319-62321 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62260 | gregory.p.smith | 2008-04-10 01:11:56 +0200 (Thu, 10 Apr 2008) | 2 lines better diagnostics ........ r62261 | gregory.p.smith | 2008-04-10 01:16:37 +0200 (Thu, 10 Apr 2008) | 3 lines Raise SystemError when size < 0 is passed into PyString_FromStringAndSize, PyBytes_FromStringAndSize or PyUnicode_FromStringAndSize. [issue2587] ........ r62266 | neal.norwitz | 2008-04-10 07:46:39 +0200 (Thu, 10 Apr 2008) | 5 lines Remove the test file before writing it in case there is no write permission. This might help fix some of the failures on Windows box(es). It doesn't hurt either way and ensure the tests are a little more self contained (ie have less assumptions). ........ r62271 | gregory.p.smith | 2008-04-10 21:50:36 +0200 (Thu, 10 Apr 2008) | 2 lines get rid of assert (size >= 0) now that an explicit if (size < 0) is in the code. ........ r62277 | andrew.kuchling | 2008-04-10 23:27:10 +0200 (Thu, 10 Apr 2008) | 1 line Remove forward-looking statement ........ r62278 | andrew.kuchling | 2008-04-10 23:28:51 +0200 (Thu, 10 Apr 2008) | 1 line Add punctuation ........ r62279 | andrew.kuchling | 2008-04-10 23:29:01 +0200 (Thu, 10 Apr 2008) | 1 line Use issue directive ........ r62289 | thomas.heller | 2008-04-11 15:05:38 +0200 (Fri, 11 Apr 2008) | 3 lines Move backwards compatibility macro to the correct place; PyIndex_Check() was introduced in Python 2.5. ........ r62290 | thomas.heller | 2008-04-11 16:20:26 +0200 (Fri, 11 Apr 2008) | 2 lines Performance improvements. ........ r62293 | christian.heimes | 2008-04-12 15:03:03 +0200 (Sat, 12 Apr 2008) | 2 lines Applied patch #2617 from Frank Wierzbicki wit some extras from me -J and -X are now reserved for Jython and non-standard arguments (e.g. IronPython). I've added some extra comments to make sure the reservation don't get missed in the future. ........ r62294 | georg.brandl | 2008-04-12 20:11:18 +0200 (Sat, 12 Apr 2008) | 2 lines Use absolute path in sys.path. ........ r62295 | georg.brandl | 2008-04-12 20:36:09 +0200 (Sat, 12 Apr 2008) | 2 lines #2615: small consistency update by Jeroen Ruigrok van der Werven. ........ r62296 | georg.brandl | 2008-04-12 21:00:20 +0200 (Sat, 12 Apr 2008) | 2 lines Add Jeroen. ........ r62297 | georg.brandl | 2008-04-12 21:05:37 +0200 (Sat, 12 Apr 2008) | 2 lines Don't offend snake lovers. ........ r62298 | gregory.p.smith | 2008-04-12 22:37:48 +0200 (Sat, 12 Apr 2008) | 2 lines fix compiler warnings ........ r62302 | gregory.p.smith | 2008-04-13 00:24:04 +0200 (Sun, 13 Apr 2008) | 3 lines socket.error inherits from IOError, it no longer needs listing in the all_errors tuple. ........ r62303 | brett.cannon | 2008-04-13 01:44:07 +0200 (Sun, 13 Apr 2008) | 8 lines Re-implement the 'warnings' module in C. This allows for usage of the 'warnings' code in places where it was previously not possible (e.g., the parser). It could also potentially lead to a speed-up in interpreter start-up if the C version of the code (_warnings) is imported over the use of the Python version in key places. Closes issue #1631171. ........ r62304 | gregory.p.smith | 2008-04-13 02:03:25 +0200 (Sun, 13 Apr 2008) | 3 lines Adds a profile-opt target for easy compilation of a python binary using gcc's profile guided optimization. ........ r62305 | brett.cannon | 2008-04-13 02:18:44 +0200 (Sun, 13 Apr 2008) | 3 lines Fix a bug in PySys_HasWarnOption() where it was not properly checking the length of the list storing the warning options. ........ r62306 | brett.cannon | 2008-04-13 02:25:15 +0200 (Sun, 13 Apr 2008) | 2 lines Fix an accidental bug of an non-existent init function. ........ r62308 | andrew.kuchling | 2008-04-13 03:05:59 +0200 (Sun, 13 Apr 2008) | 1 line Mention -J, -X ........ r62311 | benjamin.peterson | 2008-04-13 04:20:05 +0200 (Sun, 13 Apr 2008) | 2 lines Give the "Interactive Interpreter Changes" section in 2.6 whatsnew a unique link name ........ r62313 | brett.cannon | 2008-04-13 04:42:36 +0200 (Sun, 13 Apr 2008) | 3 lines Fix test_warnings by making the state of things more consistent for each test when it is run. ........ r62314 | skip.montanaro | 2008-04-13 05:17:30 +0200 (Sun, 13 Apr 2008) | 2 lines spelling ........ r62315 | georg.brandl | 2008-04-13 09:07:44 +0200 (Sun, 13 Apr 2008) | 2 lines Fix markup. ........ r62319 | christian.heimes | 2008-04-13 11:30:17 +0200 (Sun, 13 Apr 2008) | 1 line Fix compiler warning Include/warnings.h:19:28: warning: no newline at end of file ........ r62320 | christian.heimes | 2008-04-13 11:33:24 +0200 (Sun, 13 Apr 2008) | 1 line Use PyString_InternFromString instead of PyString_FromString for static vars ........ r62321 | christian.heimes | 2008-04-13 11:37:05 +0200 (Sun, 13 Apr 2008) | 1 line Added new files to the pcbuild files ........
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``formatwarning(message, category, filename, lineno, line)`` and writes the
resulting string to *file*, which defaults to :data:`sys.stderr`. You may replace
this function with any callable by assigning to ``warnings.showwarning``.
Merged revisions 62954-62959,62961,62963-62967,62969-62970,62972-62973,62975-62976,62978-62982,62984,62987-62996 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62954 | martin.v.loewis | 2008-05-09 16:11:37 -0400 (Fri, 09 May 2008) | 1 line Port to VS 2008. Drop W9x support. ........ r62957 | benjamin.peterson | 2008-05-09 17:30:26 -0400 (Fri, 09 May 2008) | 2 lines In stdtypes.rst, move methods under class directives where applicable ........ r62958 | brett.cannon | 2008-05-09 17:30:36 -0400 (Fri, 09 May 2008) | 2 lines Add a todo list to the module deletion command. ........ r62963 | brett.cannon | 2008-05-09 18:52:28 -0400 (Fri, 09 May 2008) | 2 lines Add support for extension modules in 3.0 deprection command. ........ r62967 | brett.cannon | 2008-05-09 22:25:00 -0400 (Fri, 09 May 2008) | 2 lines Fix some errors in the deprecation warnings for new and user. ........ r62975 | brett.cannon | 2008-05-09 22:54:52 -0400 (Fri, 09 May 2008) | 3 lines Suppress deprecations for packages as well when using test.test_support.import_module(). ........ r62976 | brett.cannon | 2008-05-09 22:57:03 -0400 (Fri, 09 May 2008) | 2 lines Also ignore package deprecations. ........ r62982 | benjamin.peterson | 2008-05-09 23:08:17 -0400 (Fri, 09 May 2008) | 2 lines Add the examples in the json module docstring as a doctest ........ r62992 | martin.v.loewis | 2008-05-10 09:24:09 -0400 (Sat, 10 May 2008) | 2 lines Explicitly refer to current hhp file (2.6a3) ........ r62993 | skip.montanaro | 2008-05-10 10:48:49 -0400 (Sat, 10 May 2008) | 2 lines Note the PyPI-edness of bsddb185 for people who might still need it. ........ r62994 | andrew.kuchling | 2008-05-10 13:36:24 -0400 (Sat, 10 May 2008) | 1 line Docstring typo ........ r62995 | andrew.kuchling | 2008-05-10 13:37:05 -0400 (Sat, 10 May 2008) | 1 line Document the 'line' argument ........ r62996 | andrew.kuchling | 2008-05-10 13:48:45 -0400 (Sat, 10 May 2008) | 1 line #1625509: describe behaviour of import lock ........
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*line* is a line of source code to be included in the warning
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message; if *line* is not supplied, :func:`showwarning` will
Merged revisions 62954-62959,62961,62963-62967,62969-62970,62972-62973,62975-62976,62978-62982,62984,62987-62996 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62954 | martin.v.loewis | 2008-05-09 16:11:37 -0400 (Fri, 09 May 2008) | 1 line Port to VS 2008. Drop W9x support. ........ r62957 | benjamin.peterson | 2008-05-09 17:30:26 -0400 (Fri, 09 May 2008) | 2 lines In stdtypes.rst, move methods under class directives where applicable ........ r62958 | brett.cannon | 2008-05-09 17:30:36 -0400 (Fri, 09 May 2008) | 2 lines Add a todo list to the module deletion command. ........ r62963 | brett.cannon | 2008-05-09 18:52:28 -0400 (Fri, 09 May 2008) | 2 lines Add support for extension modules in 3.0 deprection command. ........ r62967 | brett.cannon | 2008-05-09 22:25:00 -0400 (Fri, 09 May 2008) | 2 lines Fix some errors in the deprecation warnings for new and user. ........ r62975 | brett.cannon | 2008-05-09 22:54:52 -0400 (Fri, 09 May 2008) | 3 lines Suppress deprecations for packages as well when using test.test_support.import_module(). ........ r62976 | brett.cannon | 2008-05-09 22:57:03 -0400 (Fri, 09 May 2008) | 2 lines Also ignore package deprecations. ........ r62982 | benjamin.peterson | 2008-05-09 23:08:17 -0400 (Fri, 09 May 2008) | 2 lines Add the examples in the json module docstring as a doctest ........ r62992 | martin.v.loewis | 2008-05-10 09:24:09 -0400 (Sat, 10 May 2008) | 2 lines Explicitly refer to current hhp file (2.6a3) ........ r62993 | skip.montanaro | 2008-05-10 10:48:49 -0400 (Sat, 10 May 2008) | 2 lines Note the PyPI-edness of bsddb185 for people who might still need it. ........ r62994 | andrew.kuchling | 2008-05-10 13:36:24 -0400 (Sat, 10 May 2008) | 1 line Docstring typo ........ r62995 | andrew.kuchling | 2008-05-10 13:37:05 -0400 (Sat, 10 May 2008) | 1 line Document the 'line' argument ........ r62996 | andrew.kuchling | 2008-05-10 13:48:45 -0400 (Sat, 10 May 2008) | 1 line #1625509: describe behaviour of import lock ........
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try to read the line specified by *filename* and *lineno*.
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.. function:: formatwarning(message, category, filename, lineno, line=None)
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Merged revisions 74277,74321,74323,74326,74355,74465,74467,74488,74492,74513,74531,74549,74553,74625,74632,74643-74644,74647,74652,74666,74671,74727,74739 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74277 | sean.reifschneider | 2009-08-01 18:54:55 -0500 (Sat, 01 Aug 2009) | 3 lines - Issue #6624: yArg_ParseTuple with "s" format when parsing argument with NUL: Bogus TypeError detail string. ........ r74321 | guilherme.polo | 2009-08-05 11:51:41 -0500 (Wed, 05 Aug 2009) | 1 line Easier reference to find (at least while svn continues being used). ........ r74323 | guilherme.polo | 2009-08-05 18:48:26 -0500 (Wed, 05 Aug 2009) | 1 line Typo. ........ r74326 | jesse.noller | 2009-08-05 21:05:56 -0500 (Wed, 05 Aug 2009) | 1 line Fix issue 4660: spurious task_done errors in multiprocessing, remove doc note for from_address ........ r74355 | gregory.p.smith | 2009-08-12 12:02:37 -0500 (Wed, 12 Aug 2009) | 2 lines comment typo fix ........ r74465 | vinay.sajip | 2009-08-15 18:23:12 -0500 (Sat, 15 Aug 2009) | 1 line Added section on logging to one file from multiple processes. ........ r74467 | vinay.sajip | 2009-08-15 18:34:47 -0500 (Sat, 15 Aug 2009) | 1 line Refined section on logging to one file from multiple processes. ........ r74488 | vinay.sajip | 2009-08-17 08:14:37 -0500 (Mon, 17 Aug 2009) | 1 line Further refined section on logging to one file from multiple processes. ........ r74492 | r.david.murray | 2009-08-17 14:26:49 -0500 (Mon, 17 Aug 2009) | 2 lines Issue 6685: 'toupper' -> 'upper' in cgi doc example explanation. ........ r74513 | skip.montanaro | 2009-08-18 09:37:52 -0500 (Tue, 18 Aug 2009) | 1 line missing module ref (issue6723) ........ r74531 | vinay.sajip | 2009-08-20 17:04:32 -0500 (Thu, 20 Aug 2009) | 1 line Added section on exceptions raised during logging. ........ r74549 | benjamin.peterson | 2009-08-24 12:42:36 -0500 (Mon, 24 Aug 2009) | 1 line fix pdf building by teaching latex the right encoding package ........ r74553 | r.david.murray | 2009-08-26 20:04:59 -0500 (Wed, 26 Aug 2009) | 2 lines Remove leftover text from end of sentence. ........ r74625 | benjamin.peterson | 2009-09-01 17:27:57 -0500 (Tue, 01 Sep 2009) | 1 line remove the check that classmethod's argument is a callable ........ r74632 | georg.brandl | 2009-09-03 02:27:26 -0500 (Thu, 03 Sep 2009) | 1 line #6828: fix wrongly highlighted blocks. ........ r74643 | georg.brandl | 2009-09-04 01:59:20 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #2666: Handle BROWSER environment variable properly for unknown browser names in the webbrowser module. ........ r74644 | georg.brandl | 2009-09-04 02:55:14 -0500 (Fri, 04 Sep 2009) | 1 line #5047: remove Monterey support from configure. ........ r74647 | georg.brandl | 2009-09-04 03:17:04 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #5275: In Cookie's Cookie.load(), properly handle non-string arguments as documented. ........ r74652 | georg.brandl | 2009-09-04 06:25:37 -0500 (Fri, 04 Sep 2009) | 1 line #6756: add some info about the "acct" parameter. ........ r74666 | georg.brandl | 2009-09-05 04:04:09 -0500 (Sat, 05 Sep 2009) | 1 line #6841: remove duplicated word. ........ r74671 | georg.brandl | 2009-09-05 11:47:17 -0500 (Sat, 05 Sep 2009) | 1 line #6843: add link from filterwarnings to where the meaning of the arguments is covered. ........ r74727 | benjamin.peterson | 2009-09-08 18:04:22 -0500 (Tue, 08 Sep 2009) | 1 line #6865 fix ref counting in initialization of pwd module ........ r74739 | georg.brandl | 2009-09-11 02:55:20 -0500 (Fri, 11 Sep 2009) | 1 line Move function back to its section. ........
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Format a warning the standard way. This returns a string which may contain
embedded newlines and ends in a newline. *line* is a line of source code to
be included in the warning message; if *line* is not supplied,
:func:`formatwarning` will try to read the line specified by *filename* and
*lineno*.
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.. function:: filterwarnings(action, message='', category=Warning, module='', lineno=0, append=False)
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Merged revisions 74277,74321,74323,74326,74355,74465,74467,74488,74492,74513,74531,74549,74553,74625,74632,74643-74644,74647,74652,74666,74671,74727,74739 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74277 | sean.reifschneider | 2009-08-01 18:54:55 -0500 (Sat, 01 Aug 2009) | 3 lines - Issue #6624: yArg_ParseTuple with "s" format when parsing argument with NUL: Bogus TypeError detail string. ........ r74321 | guilherme.polo | 2009-08-05 11:51:41 -0500 (Wed, 05 Aug 2009) | 1 line Easier reference to find (at least while svn continues being used). ........ r74323 | guilherme.polo | 2009-08-05 18:48:26 -0500 (Wed, 05 Aug 2009) | 1 line Typo. ........ r74326 | jesse.noller | 2009-08-05 21:05:56 -0500 (Wed, 05 Aug 2009) | 1 line Fix issue 4660: spurious task_done errors in multiprocessing, remove doc note for from_address ........ r74355 | gregory.p.smith | 2009-08-12 12:02:37 -0500 (Wed, 12 Aug 2009) | 2 lines comment typo fix ........ r74465 | vinay.sajip | 2009-08-15 18:23:12 -0500 (Sat, 15 Aug 2009) | 1 line Added section on logging to one file from multiple processes. ........ r74467 | vinay.sajip | 2009-08-15 18:34:47 -0500 (Sat, 15 Aug 2009) | 1 line Refined section on logging to one file from multiple processes. ........ r74488 | vinay.sajip | 2009-08-17 08:14:37 -0500 (Mon, 17 Aug 2009) | 1 line Further refined section on logging to one file from multiple processes. ........ r74492 | r.david.murray | 2009-08-17 14:26:49 -0500 (Mon, 17 Aug 2009) | 2 lines Issue 6685: 'toupper' -> 'upper' in cgi doc example explanation. ........ r74513 | skip.montanaro | 2009-08-18 09:37:52 -0500 (Tue, 18 Aug 2009) | 1 line missing module ref (issue6723) ........ r74531 | vinay.sajip | 2009-08-20 17:04:32 -0500 (Thu, 20 Aug 2009) | 1 line Added section on exceptions raised during logging. ........ r74549 | benjamin.peterson | 2009-08-24 12:42:36 -0500 (Mon, 24 Aug 2009) | 1 line fix pdf building by teaching latex the right encoding package ........ r74553 | r.david.murray | 2009-08-26 20:04:59 -0500 (Wed, 26 Aug 2009) | 2 lines Remove leftover text from end of sentence. ........ r74625 | benjamin.peterson | 2009-09-01 17:27:57 -0500 (Tue, 01 Sep 2009) | 1 line remove the check that classmethod's argument is a callable ........ r74632 | georg.brandl | 2009-09-03 02:27:26 -0500 (Thu, 03 Sep 2009) | 1 line #6828: fix wrongly highlighted blocks. ........ r74643 | georg.brandl | 2009-09-04 01:59:20 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #2666: Handle BROWSER environment variable properly for unknown browser names in the webbrowser module. ........ r74644 | georg.brandl | 2009-09-04 02:55:14 -0500 (Fri, 04 Sep 2009) | 1 line #5047: remove Monterey support from configure. ........ r74647 | georg.brandl | 2009-09-04 03:17:04 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #5275: In Cookie's Cookie.load(), properly handle non-string arguments as documented. ........ r74652 | georg.brandl | 2009-09-04 06:25:37 -0500 (Fri, 04 Sep 2009) | 1 line #6756: add some info about the "acct" parameter. ........ r74666 | georg.brandl | 2009-09-05 04:04:09 -0500 (Sat, 05 Sep 2009) | 1 line #6841: remove duplicated word. ........ r74671 | georg.brandl | 2009-09-05 11:47:17 -0500 (Sat, 05 Sep 2009) | 1 line #6843: add link from filterwarnings to where the meaning of the arguments is covered. ........ r74727 | benjamin.peterson | 2009-09-08 18:04:22 -0500 (Tue, 08 Sep 2009) | 1 line #6865 fix ref counting in initialization of pwd module ........ r74739 | georg.brandl | 2009-09-11 02:55:20 -0500 (Fri, 11 Sep 2009) | 1 line Move function back to its section. ........
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Insert an entry into the list of :ref:`warnings filter specifications
<warning-filter>`. The entry is inserted at the front by default; if
*append* is true, it is inserted at the end. This checks the types of the
arguments, compiles the *message* and *module* regular expressions, and
inserts them as a tuple in the list of warnings filters. Entries closer to
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the front of the list override entries later in the list, if both match a
particular warning. Omitted arguments default to a value that matches
everything.
.. function:: simplefilter(action, category=Warning, lineno=0, append=False)
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Merged revisions 74277,74321,74323,74326,74355,74465,74467,74488,74492,74513,74531,74549,74553,74625,74632,74643-74644,74647,74652,74666,74671,74727,74739 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74277 | sean.reifschneider | 2009-08-01 18:54:55 -0500 (Sat, 01 Aug 2009) | 3 lines - Issue #6624: yArg_ParseTuple with "s" format when parsing argument with NUL: Bogus TypeError detail string. ........ r74321 | guilherme.polo | 2009-08-05 11:51:41 -0500 (Wed, 05 Aug 2009) | 1 line Easier reference to find (at least while svn continues being used). ........ r74323 | guilherme.polo | 2009-08-05 18:48:26 -0500 (Wed, 05 Aug 2009) | 1 line Typo. ........ r74326 | jesse.noller | 2009-08-05 21:05:56 -0500 (Wed, 05 Aug 2009) | 1 line Fix issue 4660: spurious task_done errors in multiprocessing, remove doc note for from_address ........ r74355 | gregory.p.smith | 2009-08-12 12:02:37 -0500 (Wed, 12 Aug 2009) | 2 lines comment typo fix ........ r74465 | vinay.sajip | 2009-08-15 18:23:12 -0500 (Sat, 15 Aug 2009) | 1 line Added section on logging to one file from multiple processes. ........ r74467 | vinay.sajip | 2009-08-15 18:34:47 -0500 (Sat, 15 Aug 2009) | 1 line Refined section on logging to one file from multiple processes. ........ r74488 | vinay.sajip | 2009-08-17 08:14:37 -0500 (Mon, 17 Aug 2009) | 1 line Further refined section on logging to one file from multiple processes. ........ r74492 | r.david.murray | 2009-08-17 14:26:49 -0500 (Mon, 17 Aug 2009) | 2 lines Issue 6685: 'toupper' -> 'upper' in cgi doc example explanation. ........ r74513 | skip.montanaro | 2009-08-18 09:37:52 -0500 (Tue, 18 Aug 2009) | 1 line missing module ref (issue6723) ........ r74531 | vinay.sajip | 2009-08-20 17:04:32 -0500 (Thu, 20 Aug 2009) | 1 line Added section on exceptions raised during logging. ........ r74549 | benjamin.peterson | 2009-08-24 12:42:36 -0500 (Mon, 24 Aug 2009) | 1 line fix pdf building by teaching latex the right encoding package ........ r74553 | r.david.murray | 2009-08-26 20:04:59 -0500 (Wed, 26 Aug 2009) | 2 lines Remove leftover text from end of sentence. ........ r74625 | benjamin.peterson | 2009-09-01 17:27:57 -0500 (Tue, 01 Sep 2009) | 1 line remove the check that classmethod's argument is a callable ........ r74632 | georg.brandl | 2009-09-03 02:27:26 -0500 (Thu, 03 Sep 2009) | 1 line #6828: fix wrongly highlighted blocks. ........ r74643 | georg.brandl | 2009-09-04 01:59:20 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #2666: Handle BROWSER environment variable properly for unknown browser names in the webbrowser module. ........ r74644 | georg.brandl | 2009-09-04 02:55:14 -0500 (Fri, 04 Sep 2009) | 1 line #5047: remove Monterey support from configure. ........ r74647 | georg.brandl | 2009-09-04 03:17:04 -0500 (Fri, 04 Sep 2009) | 2 lines Issue #5275: In Cookie's Cookie.load(), properly handle non-string arguments as documented. ........ r74652 | georg.brandl | 2009-09-04 06:25:37 -0500 (Fri, 04 Sep 2009) | 1 line #6756: add some info about the "acct" parameter. ........ r74666 | georg.brandl | 2009-09-05 04:04:09 -0500 (Sat, 05 Sep 2009) | 1 line #6841: remove duplicated word. ........ r74671 | georg.brandl | 2009-09-05 11:47:17 -0500 (Sat, 05 Sep 2009) | 1 line #6843: add link from filterwarnings to where the meaning of the arguments is covered. ........ r74727 | benjamin.peterson | 2009-09-08 18:04:22 -0500 (Tue, 08 Sep 2009) | 1 line #6865 fix ref counting in initialization of pwd module ........ r74739 | georg.brandl | 2009-09-11 02:55:20 -0500 (Fri, 11 Sep 2009) | 1 line Move function back to its section. ........
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Insert a simple entry into the list of :ref:`warnings filter specifications
<warning-filter>`. The meaning of the function parameters is as for
:func:`filterwarnings`, but regular expressions are not needed as the filter
inserted always matches any message in any module as long as the category and
line number match.
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.. function:: resetwarnings()
Reset the warnings filter. This discards the effect of all previous calls to
:func:`filterwarnings`, including that of the :option:`-W` command line options
and calls to :func:`simplefilter`.
Available Context Managers
--------------------------
.. class:: catch_warnings(*, record=False, module=None, action=None, category=Warning, lineno=0, append=False)
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A context manager that copies and, upon exit, restores the warnings filter
and the :func:`showwarning` function.
If the *record* argument is :const:`False` (the default) the context manager
returns :class:`None` on entry. If *record* is :const:`True`, a list is
returned that is progressively populated with objects as seen by a custom
:func:`showwarning` function (which also suppresses output to ``sys.stdout``).
Each object in the list has attributes with the same names as the arguments to
:func:`showwarning`.
The *module* argument takes a module that will be used instead of the
module returned when you import :mod:`warnings` whose filter will be
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protected. This argument exists primarily for testing the :mod:`warnings`
module itself.
Merged revisions 79307,79408,79430,79533,79542,79579-79580,79585-79587,79607-79608,79622,79717,79820,79822,79828,79862,79875,79923-79924,79941-79943,79945,79947,79951-79952 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r79307 | florent.xicluna | 2010-03-22 17:45:50 -0500 (Mon, 22 Mar 2010) | 2 lines #7667: Fix doctest failures with non-ASCII paths. ........ r79408 | victor.stinner | 2010-03-24 20:18:38 -0500 (Wed, 24 Mar 2010) | 2 lines Fix a gcc warning introduced by r79397. ........ r79430 | brian.curtin | 2010-03-25 18:48:54 -0500 (Thu, 25 Mar 2010) | 2 lines Fix #6538. Markup RegexObject and MatchObject as classes. Patch by Ryan Arana. ........ r79533 | barry.warsaw | 2010-03-31 16:07:16 -0500 (Wed, 31 Mar 2010) | 6 lines - Issue #8233: When run as a script, py_compile.py optionally takes a single argument `-` which tells it to read files to compile from stdin. Each line is read on demand and the named file is compiled immediately. (Original patch by Piotr O?\197?\188arowski). ........ r79542 | r.david.murray | 2010-03-31 20:28:39 -0500 (Wed, 31 Mar 2010) | 3 lines A couple small grammar fixes in test.rst, and rewrite the check_warnings docs to be clearer. ........ r79579 | georg.brandl | 2010-04-02 03:34:41 -0500 (Fri, 02 Apr 2010) | 1 line Add 2.6.5. ........ r79580 | georg.brandl | 2010-04-02 03:39:09 -0500 (Fri, 02 Apr 2010) | 1 line #2768: add a note on how to get a file descriptor. ........ r79585 | georg.brandl | 2010-04-02 04:03:18 -0500 (Fri, 02 Apr 2010) | 1 line Remove col-spanning cells in logging docs. ........ r79586 | georg.brandl | 2010-04-02 04:07:42 -0500 (Fri, 02 Apr 2010) | 1 line Document PyImport_ExecCodeModuleEx(). ........ r79587 | georg.brandl | 2010-04-02 04:11:49 -0500 (Fri, 02 Apr 2010) | 1 line #8012: clarification in generator glossary entry. ........ r79607 | andrew.kuchling | 2010-04-02 12:48:23 -0500 (Fri, 02 Apr 2010) | 1 line #6647: document that catch_warnings is not thread-safe ........ r79608 | andrew.kuchling | 2010-04-02 12:54:26 -0500 (Fri, 02 Apr 2010) | 1 line #6647: add note to two examples ........ r79622 | tarek.ziade | 2010-04-02 16:34:19 -0500 (Fri, 02 Apr 2010) | 1 line removed documentation on code that was reverted and pushed into distutils2 ........ r79717 | antoine.pitrou | 2010-04-03 16:22:38 -0500 (Sat, 03 Apr 2010) | 4 lines Fix wording / typography, and a slightly misleading statement (memoryviews don't support complex structures right now) ........ r79820 | benjamin.peterson | 2010-04-05 22:34:09 -0500 (Mon, 05 Apr 2010) | 1 line ready _sre types ........ r79822 | georg.brandl | 2010-04-06 03:18:15 -0500 (Tue, 06 Apr 2010) | 1 line #8320: document return value of recv_into(). ........ r79828 | georg.brandl | 2010-04-06 09:33:44 -0500 (Tue, 06 Apr 2010) | 1 line Add JP. ........ r79862 | georg.brandl | 2010-04-06 15:27:59 -0500 (Tue, 06 Apr 2010) | 1 line Fix syntax. ........ r79875 | mark.dickinson | 2010-04-06 17:18:23 -0500 (Tue, 06 Apr 2010) | 1 line More NaN consistency doc fixes. ........ r79923 | georg.brandl | 2010-04-10 06:15:24 -0500 (Sat, 10 Apr 2010) | 1 line #8360: skipTest was added in 2.7. ........ r79924 | georg.brandl | 2010-04-10 06:16:59 -0500 (Sat, 10 Apr 2010) | 1 line #8346: update version. ........ r79941 | andrew.kuchling | 2010-04-10 20:39:36 -0500 (Sat, 10 Apr 2010) | 1 line Two grammar fixes ........ r79942 | andrew.kuchling | 2010-04-10 20:40:06 -0500 (Sat, 10 Apr 2010) | 1 line Punctuation fix ........ r79943 | andrew.kuchling | 2010-04-10 20:40:30 -0500 (Sat, 10 Apr 2010) | 1 line Add various items ........ r79945 | andrew.kuchling | 2010-04-10 20:40:49 -0500 (Sat, 10 Apr 2010) | 1 line name correct ........ r79947 | andrew.kuchling | 2010-04-10 20:44:13 -0500 (Sat, 10 Apr 2010) | 1 line Remove distutils section ........ r79951 | andrew.kuchling | 2010-04-11 07:48:08 -0500 (Sun, 11 Apr 2010) | 1 line Two typo fixes ........ r79952 | andrew.kuchling | 2010-04-11 07:49:37 -0500 (Sun, 11 Apr 2010) | 1 line Add two items ........
2010-04-11 13:12:57 -03:00
If the *action* argument is not ``None``, the remaining arguments are
passed to :func:`simplefilter` as if it were called immediately on
entering the context.
Merged revisions 79307,79408,79430,79533,79542,79579-79580,79585-79587,79607-79608,79622,79717,79820,79822,79828,79862,79875,79923-79924,79941-79943,79945,79947,79951-79952 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r79307 | florent.xicluna | 2010-03-22 17:45:50 -0500 (Mon, 22 Mar 2010) | 2 lines #7667: Fix doctest failures with non-ASCII paths. ........ r79408 | victor.stinner | 2010-03-24 20:18:38 -0500 (Wed, 24 Mar 2010) | 2 lines Fix a gcc warning introduced by r79397. ........ r79430 | brian.curtin | 2010-03-25 18:48:54 -0500 (Thu, 25 Mar 2010) | 2 lines Fix #6538. Markup RegexObject and MatchObject as classes. Patch by Ryan Arana. ........ r79533 | barry.warsaw | 2010-03-31 16:07:16 -0500 (Wed, 31 Mar 2010) | 6 lines - Issue #8233: When run as a script, py_compile.py optionally takes a single argument `-` which tells it to read files to compile from stdin. Each line is read on demand and the named file is compiled immediately. (Original patch by Piotr O?\197?\188arowski). ........ r79542 | r.david.murray | 2010-03-31 20:28:39 -0500 (Wed, 31 Mar 2010) | 3 lines A couple small grammar fixes in test.rst, and rewrite the check_warnings docs to be clearer. ........ r79579 | georg.brandl | 2010-04-02 03:34:41 -0500 (Fri, 02 Apr 2010) | 1 line Add 2.6.5. ........ r79580 | georg.brandl | 2010-04-02 03:39:09 -0500 (Fri, 02 Apr 2010) | 1 line #2768: add a note on how to get a file descriptor. ........ r79585 | georg.brandl | 2010-04-02 04:03:18 -0500 (Fri, 02 Apr 2010) | 1 line Remove col-spanning cells in logging docs. ........ r79586 | georg.brandl | 2010-04-02 04:07:42 -0500 (Fri, 02 Apr 2010) | 1 line Document PyImport_ExecCodeModuleEx(). ........ r79587 | georg.brandl | 2010-04-02 04:11:49 -0500 (Fri, 02 Apr 2010) | 1 line #8012: clarification in generator glossary entry. ........ r79607 | andrew.kuchling | 2010-04-02 12:48:23 -0500 (Fri, 02 Apr 2010) | 1 line #6647: document that catch_warnings is not thread-safe ........ r79608 | andrew.kuchling | 2010-04-02 12:54:26 -0500 (Fri, 02 Apr 2010) | 1 line #6647: add note to two examples ........ r79622 | tarek.ziade | 2010-04-02 16:34:19 -0500 (Fri, 02 Apr 2010) | 1 line removed documentation on code that was reverted and pushed into distutils2 ........ r79717 | antoine.pitrou | 2010-04-03 16:22:38 -0500 (Sat, 03 Apr 2010) | 4 lines Fix wording / typography, and a slightly misleading statement (memoryviews don't support complex structures right now) ........ r79820 | benjamin.peterson | 2010-04-05 22:34:09 -0500 (Mon, 05 Apr 2010) | 1 line ready _sre types ........ r79822 | georg.brandl | 2010-04-06 03:18:15 -0500 (Tue, 06 Apr 2010) | 1 line #8320: document return value of recv_into(). ........ r79828 | georg.brandl | 2010-04-06 09:33:44 -0500 (Tue, 06 Apr 2010) | 1 line Add JP. ........ r79862 | georg.brandl | 2010-04-06 15:27:59 -0500 (Tue, 06 Apr 2010) | 1 line Fix syntax. ........ r79875 | mark.dickinson | 2010-04-06 17:18:23 -0500 (Tue, 06 Apr 2010) | 1 line More NaN consistency doc fixes. ........ r79923 | georg.brandl | 2010-04-10 06:15:24 -0500 (Sat, 10 Apr 2010) | 1 line #8360: skipTest was added in 2.7. ........ r79924 | georg.brandl | 2010-04-10 06:16:59 -0500 (Sat, 10 Apr 2010) | 1 line #8346: update version. ........ r79941 | andrew.kuchling | 2010-04-10 20:39:36 -0500 (Sat, 10 Apr 2010) | 1 line Two grammar fixes ........ r79942 | andrew.kuchling | 2010-04-10 20:40:06 -0500 (Sat, 10 Apr 2010) | 1 line Punctuation fix ........ r79943 | andrew.kuchling | 2010-04-10 20:40:30 -0500 (Sat, 10 Apr 2010) | 1 line Add various items ........ r79945 | andrew.kuchling | 2010-04-10 20:40:49 -0500 (Sat, 10 Apr 2010) | 1 line name correct ........ r79947 | andrew.kuchling | 2010-04-10 20:44:13 -0500 (Sat, 10 Apr 2010) | 1 line Remove distutils section ........ r79951 | andrew.kuchling | 2010-04-11 07:48:08 -0500 (Sun, 11 Apr 2010) | 1 line Two typo fixes ........ r79952 | andrew.kuchling | 2010-04-11 07:49:37 -0500 (Sun, 11 Apr 2010) | 1 line Add two items ........
2010-04-11 13:12:57 -03:00
.. note::
The :class:`catch_warnings` manager works by replacing and
then later restoring the module's
:func:`showwarning` function and internal list of filter
specifications. This means the context manager is modifying
global state and therefore is not thread-safe.
.. versionchanged:: 3.11
Added the *action*, *category*, *lineno*, and *append* parameters.