Name	Size	Mode	Actions
2to3.rst.txt	14647	0644	editdlrm
abc.rst.txt	7219	0644	editdlrm
aepack.rst.txt	4257	0644	editdlrm
aetools.rst.txt	3532	0644	editdlrm
aetypes.rst.txt	4257	0644	editdlrm
aifc.rst.txt	7086	0644	editdlrm
al.rst.txt	5309	0644	editdlrm
allos.rst.txt	695	0644	editdlrm
anydbm.rst.txt	4111	0644	editdlrm
archiving.rst.txt	424	0644	editdlrm
argparse.rst.txt	74685	0644	editdlrm
array.rst.txt	10524	0644	editdlrm
ast.rst.txt	10111	0644	editdlrm
asynchat.rst.txt	9206	0644	editdlrm
asyncore.rst.txt	12937	0644	editdlrm
atexit.rst.txt	3910	0644	editdlrm
audioop.rst.txt	10395	0644	editdlrm
autogil.rst.txt	1015	0644	editdlrm
base64.rst.txt	6252	0644	editdlrm
basehttpserver.rst.txt	10404	0644	editdlrm
bastion.rst.txt	2611	0644	editdlrm
bdb.rst.txt	12456	0644	editdlrm
binascii.rst.txt	6508	0644	editdlrm
binhex.rst.txt	1910	0644	editdlrm
bisect.rst.txt	5415	0644	editdlrm
bsddb.rst.txt	7575	0644	editdlrm
bz2.rst.txt	8064	0644	editdlrm
calendar.rst.txt	11282	0644	editdlrm
carbon.rst.txt	15956	0644	editdlrm
cd.rst.txt	11974	0644	editdlrm
cgi.rst.txt	22853	0644	editdlrm
cgihttpserver.rst.txt	2788	0644	editdlrm
cgitb.rst.txt	2874	0644	editdlrm
chunk.rst.txt	4955	0644	editdlrm
cmath.rst.txt	7647	0644	editdlrm
cmd.rst.txt	8565	0644	editdlrm
code.rst.txt	7115	0644	editdlrm
codecs.rst.txt	66966	0644	editdlrm
codeop.rst.txt	3774	0644	editdlrm
collections.rst.txt	41448	0644	editdlrm
colorpicker.rst.txt	913	0644	editdlrm
colorsys.rst.txt	1819	0644	editdlrm
commands.rst.txt	2595	0644	editdlrm
compileall.rst.txt	4678	0644	editdlrm
compiler.rst.txt	37464	0644	editdlrm
configparser.rst.txt	19607	0644	editdlrm
constants.rst.txt	2328	0644	editdlrm
contextlib.rst.txt	6012	0644	editdlrm
cookie.rst.txt	9543	0644	editdlrm
cookielib.rst.txt	27875	0644	editdlrm
copy.rst.txt	3351	0644	editdlrm
copy_reg.rst.txt	2329	0644	editdlrm
crypt.rst.txt	2292	0644	editdlrm
crypto.rst.txt	355	0644	editdlrm
csv.rst.txt	22757	0644	editdlrm
ctypes.rst.txt	90513	0644	editdlrm
curses.ascii.rst.txt	9046	0644	editdlrm
curses.panel.rst.txt	2740	0644	editdlrm
curses.rst.txt	74877	0644	editdlrm
custominterp.rst.txt	570	0644	editdlrm
datatypes.rst.txt	864	0644	editdlrm
datetime.rst.txt	74679	0644	editdlrm
dbhash.rst.txt	3865	0644	editdlrm
dbm.rst.txt	3117	0644	editdlrm
debug.rst.txt	446	0644	editdlrm
decimal.rst.txt	70926	0644	editdlrm
development.rst.txt	640	0644	editdlrm
difflib.rst.txt	30716	0644	editdlrm
dircache.rst.txt	1813	0644	editdlrm
dis.rst.txt	23248	0644	editdlrm
distribution.rst.txt	426	0644	editdlrm
distutils.rst.txt	1958	0644	editdlrm
dl.rst.txt	3392	0644	editdlrm
doctest.rst.txt	73985	0644	editdlrm
docxmlrpcserver.rst.txt	3802	0644	editdlrm
dumbdbm.rst.txt	2841	0644	editdlrm
dummy_thread.rst.txt	1058	0644	editdlrm
dummy_threading.rst.txt	799	0644	editdlrm
easydialogs.rst.txt	10346	0644	editdlrm
email-examples.rst.txt	1271	0644	editdlrm
email.charset.rst.txt	9654	0644	editdlrm
email.encoders.rst.txt	2376	0644	editdlrm
email.errors.rst.txt	4006	0644	editdlrm
email.generator.rst.txt	6132	0644	editdlrm
email.header.rst.txt	7531	0644	editdlrm
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email.message.rst.txt	25217	0644	editdlrm
email.mime.rst.txt	9917	0644	editdlrm
email.parser.rst.txt	10327	0644	editdlrm
email.rst.txt	16111	0644	editdlrm
email.utils.rst.txt	6475	0644	editdlrm
ensurepip.rst.txt	5022	0644	editdlrm
errno.rst.txt	6708	0644	editdlrm
exceptions.rst.txt	18343	0644	editdlrm
fcntl.rst.txt	7361	0644	editdlrm
filecmp.rst.txt	5348	0644	editdlrm
fileformats.rst.txt	302	0644	editdlrm
fileinput.rst.txt	7417	0644	editdlrm
filesys.rst.txt	806	0644	editdlrm
fl.rst.txt	17646	0644	editdlrm
fm.rst.txt	2699	0644	editdlrm
fnmatch.rst.txt	3104	0644	editdlrm
formatter.rst.txt	13245	0644	editdlrm
fpectl.rst.txt	4171	0644	editdlrm
fpformat.rst.txt	1747	0644	editdlrm
fractions.rst.txt	5297	0644	editdlrm
framework.rst.txt	11444	0644	editdlrm
frameworks.rst.txt	378	0644	editdlrm
ftplib.rst.txt	15720	0644	editdlrm
functions.rst.txt	75554	0644	editdlrm
functools.rst.txt	7448	0644	editdlrm
future_builtins.rst.txt	2010	0644	editdlrm
gc.rst.txt	9014	0644	editdlrm
gdbm.rst.txt	4882	0644	editdlrm
gensuitemodule.rst.txt	3113	0644	editdlrm
getopt.rst.txt	6670	0644	editdlrm
getpass.rst.txt	1876	0644	editdlrm
gettext.rst.txt	29040	0644	editdlrm
gl.rst.txt	6009	0644	editdlrm
glob.rst.txt	2414	0644	editdlrm
grp.rst.txt	2256	0644	editdlrm
gzip.rst.txt	4828	0644	editdlrm
hashlib.rst.txt	7379	0644	editdlrm
heapq.rst.txt	13185	0644	editdlrm
hmac.rst.txt	3073	0644	editdlrm
hotshot.rst.txt	4289	0644	editdlrm
htmllib.rst.txt	7379	0644	editdlrm
htmlparser.rst.txt	11640	0644	editdlrm
httplib.rst.txt	37454	0644	editdlrm
i18n.rst.txt	409	0644	editdlrm
ic.rst.txt	5005	0644	editdlrm
idle.rst.txt	22182	0644	editdlrm
imageop.rst.txt	4001	0644	editdlrm
imaplib.rst.txt	17221	0644	editdlrm
imgfile.rst.txt	2765	0644	editdlrm
imghdr.rst.txt	2635	0644	editdlrm
imp.rst.txt	12593	0644	editdlrm
importlib.rst.txt	1126	0644	editdlrm
imputil.rst.txt	7023	0644	editdlrm
index.rst.txt	2287	0644	editdlrm
inspect.rst.txt	28151	0644	editdlrm
internet.rst.txt	950	0644	editdlrm
intro.rst.txt	2803	0644	editdlrm
io.rst.txt	39015	0644	editdlrm
ipc.rst.txt	630	0644	editdlrm
itertools.rst.txt	36324	0644	editdlrm
jpeg.rst.txt	3858	0644	editdlrm
json.rst.txt	25545	0644	editdlrm
keyword.rst.txt	617	0644	editdlrm
language.rst.txt	523	0644	editdlrm
linecache.rst.txt	1887	0644	editdlrm
locale.rst.txt	24975	0644	editdlrm
logging.config.rst.txt	31560	0644	editdlrm
logging.handlers.rst.txt	28153	0644	editdlrm
logging.rst.txt	46882	0644	editdlrm
mac.rst.txt	791	0644	editdlrm
macos.rst.txt	3824	0644	editdlrm
macosa.rst.txt	3964	0644	editdlrm
macostools.rst.txt	4017	0644	editdlrm
macpath.rst.txt	650	0644	editdlrm
mailbox.rst.txt	68129	0644	editdlrm
mailcap.rst.txt	3675	0644	editdlrm
markup.rst.txt	1249	0644	editdlrm
marshal.rst.txt	5689	0644	editdlrm
math.rst.txt	10920	0644	editdlrm
md5.rst.txt	2815	0644	editdlrm
mhlib.rst.txt	3966	0644	editdlrm
mimetools.rst.txt	4504	0644	editdlrm
mimetypes.rst.txt	9839	0644	editdlrm
mimewriter.rst.txt	3360	0644	editdlrm
mimify.rst.txt	3519	0644	editdlrm
miniaeframe.rst.txt	2564	0644	editdlrm
misc.rst.txt	248	0644	editdlrm
mm.rst.txt	447	0644	editdlrm
mmap.rst.txt	10481	0644	editdlrm
modulefinder.rst.txt	3380	0644	editdlrm
modules.rst.txt	382	0644	editdlrm
msilib.rst.txt	19062	0644	editdlrm
msvcrt.rst.txt	4346	0644	editdlrm
multifile.rst.txt	6613	0644	editdlrm
multiprocessing.rst.txt	92621	0644	editdlrm
mutex.rst.txt	1939	0644	editdlrm
netdata.rst.txt	432	0644	editdlrm
netrc.rst.txt	3119	0644	editdlrm
new.rst.txt	2653	0644	editdlrm
nis.rst.txt	2108	0644	editdlrm
nntplib.rst.txt	14531	0644	editdlrm
numbers.rst.txt	8007	0644	editdlrm
numeric.rst.txt	751	0644	editdlrm
operator.rst.txt	22092	0644	editdlrm
optparse.rst.txt	77101	0644	editdlrm
os.path.rst.txt	13094	0644	editdlrm
os.rst.txt	82580	0644	editdlrm
ossaudiodev.rst.txt	17309	0644	editdlrm
othergui.rst.txt	2721	0644	editdlrm
parser.rst.txt	15385	0644	editdlrm
pdb.rst.txt	16043	0644	editdlrm
persistence.rst.txt	826	0644	editdlrm
pickle.rst.txt	37262	0644	editdlrm
pickletools.rst.txt	1997	0644	editdlrm
pipes.rst.txt	3786	0644	editdlrm
pkgutil.rst.txt	7714	0644	editdlrm
platform.rst.txt	9554	0644	editdlrm
plistlib.rst.txt	4134	0644	editdlrm
popen2.rst.txt	7022	0644	editdlrm
poplib.rst.txt	6220	0644	editdlrm
posix.rst.txt	3630	0644	editdlrm
posixfile.rst.txt	7200	0644	editdlrm
pprint.rst.txt	9071	0644	editdlrm
profile.rst.txt	28666	0644	editdlrm
pty.rst.txt	1762	0644	editdlrm
pwd.rst.txt	2725	0644	editdlrm
pyclbr.rst.txt	3296	0644	editdlrm
pydoc.rst.txt	4083	0644	editdlrm
pyexpat.rst.txt	28891	0644	editdlrm
python.rst.txt	514	0644	editdlrm
py_compile.rst.txt	2479	0644	editdlrm
queue.rst.txt	7034	0644	editdlrm
quopri.rst.txt	2670	0644	editdlrm
random.rst.txt	13319	0644	editdlrm
re.rst.txt	55102	0644	editdlrm
readline.rst.txt	10513	0644	editdlrm
repr.rst.txt	4718	0644	editdlrm
resource.rst.txt	9595	0644	editdlrm
restricted.rst.txt	3327	0644	editdlrm
rexec.rst.txt	11742	0644	editdlrm
rfc822.rst.txt	14037	0644	editdlrm
rlcompleter.rst.txt	2494	0644	editdlrm
robotparser.rst.txt	2190	0644	editdlrm
runpy.rst.txt	6938	0644	editdlrm
sched.rst.txt	4644	0644	editdlrm
scrolledtext.rst.txt	1379	0644	editdlrm
select.rst.txt	20705	0644	editdlrm
sets.rst.txt	14973	0644	editdlrm
sgi.rst.txt	322	0644	editdlrm
sgmllib.rst.txt	10664	0644	editdlrm
sha.rst.txt	2807	0644	editdlrm
shelve.rst.txt	8319	0644	editdlrm
shlex.rst.txt	11313	0644	editdlrm
shutil.rst.txt	13491	0644	editdlrm
signal.rst.txt	10719	0644	editdlrm
simplehttpserver.rst.txt	4559	0644	editdlrm
simplexmlrpcserver.rst.txt	10881	0644	editdlrm
site.rst.txt	7880	0644	editdlrm
smtpd.rst.txt	2464	0644	editdlrm
smtplib.rst.txt	14906	0644	editdlrm
sndhdr.rst.txt	1759	0644	editdlrm
socket.rst.txt	40765	0644	editdlrm
socketserver.rst.txt	22512	0644	editdlrm
someos.rst.txt	599	0644	editdlrm
spwd.rst.txt	2825	0644	editdlrm
sqlite3.rst.txt	35448	0644	editdlrm
ssl.rst.txt	76554	0644	editdlrm
stat.rst.txt	7778	0644	editdlrm
statvfs.rst.txt	1300	0644	editdlrm
stdtypes.rst.txt	122668	0644	editdlrm
string.rst.txt	44085	0644	editdlrm
stringio.rst.txt	4166	0644	editdlrm
stringprep.rst.txt	4238	0644	editdlrm
strings.rst.txt	746	0644	editdlrm
struct.rst.txt	17100	0644	editdlrm
subprocess.rst.txt	33648	0644	editdlrm
sun.rst.txt	249	0644	editdlrm
sunau.rst.txt	7124	0644	editdlrm
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sys.rst.txt	47520	0644	editdlrm
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telnetlib.rst.txt	7482	0644	editdlrm
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urllib.rst.txt	24960	0644	editdlrm
urllib2.rst.txt	35211	0644	editdlrm
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winsound.rst.txt	5066	0644	editdlrm
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xml.etree.elementtree.rst.txt	35707	0644	editdlrm
xml.rst.txt	6090	0644	editdlrm
xml.sax.handler.rst.txt	15371	0644	editdlrm
xml.sax.reader.rst.txt	12257	0644	editdlrm
xml.sax.rst.txt	6460	0644	editdlrm
xml.sax.utils.rst.txt	3560	0644	editdlrm
xmlrpclib.rst.txt	22559	0644	editdlrm
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__main__.rst.txt	535	0644	editdlrm

:mod:`warnings` --- Warning control =================================== .. index:: single: warnings .. module:: warnings :synopsis: Issue warning messages and control their disposition. .. versionadded:: 2.1 **Source code:** :source:`Lib/warnings.py` -------------- 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 :ref:`exceptionhandling` for details). Warning messages are normally written to ``sys.stderr``, but their disposition can be changed flexibly, from ignoring all warnings to turning them into exceptions. The disposition of warnings can vary based on the warning category (see below), the text of the warning message, and the source location where it 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 warning filter, which is a sequence of matching rules and actions. Rules can be 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. .. _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. The following warnings category classes are currently defined: .. tabularcolumns:: |l|p{0.6\linewidth}| +----------------------------------+-----------------------------------------------+ | 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 (ignored by default). | +----------------------------------+-----------------------------------------------+ | :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 constructs | | | that will change semantically in the future. | +----------------------------------+-----------------------------------------------+ | :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. | +----------------------------------+-----------------------------------------------+ While these are technically built-in 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. .. versionchanged:: 2.7 :exc:`DeprecationWarning` is ignored by default. .. _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 match determines 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 | +===============+==============================================+ | ``"error"`` | turn matching warnings into exceptions | +---------------+----------------------------------------------+ | ``"ignore"`` | never print matching warnings | +---------------+----------------------------------------------+ | ``"always"`` | always print matching warnings | +---------------+----------------------------------------------+ | ``"default"`` | print the first occurrence of matching | | | warnings for each location where the warning | | | is issued | +---------------+----------------------------------------------+ | ``"module"`` | print the first occurrence of matching | | | warnings for each module where the warning | | | is issued | +---------------+----------------------------------------------+ | ``"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. * *category* is a class (a subclass of :exc:`Warning`) of which the warning category must be a subclass in order to match. * *module* is a string containing a regular expression that the module name must match. The expression is compiled to be case-sensitive. * *lineno* is an integer that the line number where the warning occurred must match, or ``0`` to match all line numbers. 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)``. The warnings filter is initialized by :option:`-W` options passed to the Python interpreter command line. The interpreter saves the arguments for all :option:`-W` options without interpretation in ``sys.warnoptions``; the :mod:`warnings` module parses these when it is first imported (invalid options are ignored, after printing a message to ``sys.stderr``). Default Warning Filters ~~~~~~~~~~~~~~~~~~~~~~~ By default, Python installs several warning filters, which can be overridden by the command-line options passed to :option:`-W` and calls to :func:`filterwarnings`. * :exc:`DeprecationWarning` and :exc:`PendingDeprecationWarning`, and :exc:`ImportWarning` are ignored. * :exc:`BytesWarning` is ignored unless the :option:`-b` option is given once or twice; in this case this warning is either printed (``-b``) or turned into an exception (``-bb``). .. _warning-suppress: Temporarily Suppressing Warnings -------------------------------- 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, then it is possible to suppress 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 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 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 results. The :func:`showwarning` function in the module is also restored to 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. 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). Updating Code For New Versions of Python ---------------------------------------- Warnings that are only of interest to the developer are ignored by default. As such you should make sure to test your code with typically ignored warnings made visible. You can do this from the command-line by passing :option:`-Wd <-W>` to the interpreter (this is shorthand for :option:`!-W default`). This enables default handling for all warnings, including those that are ignored by default. To change what action is taken for encountered warnings you simply 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. To programmatically do the same as :option:`!-Wd`, use:: warnings.simplefilter('default') Make sure to execute this code as soon as possible. This prevents the registering of what warnings have been raised from unexpectedly influencing how future warnings are treated. Having certain warnings ignored by default is done to prevent a user from seeing warnings that are only of interest to the developer. As you do not necessarily have control over what interpreter a user uses to run their code, it is possible that a new version of Python will be released between your release cycles. The new interpreter release could trigger new warnings in your code that were not there in an older interpreter, e.g. :exc:`DeprecationWarning` for a module that you are using. While you as a developer want to be notified that your code is using a deprecated module, to a user this information is essentially noise and provides no benefit to them. .. _warning-functions: Available Functions ------------------- .. function:: warn(message[, category[, stacklevel]]) Issue a warning, or maybe ignore it or raise an exception. The *category* argument, if given, must be a warning category class (see above); it defaults to :exc:`UserWarning`. Alternatively *message* can be a :exc:`Warning` instance, 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 exception if the particular warning issued is changed into an error by the warnings filter see above. The *stacklevel* argument can be used by wrapper 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). .. function:: warn_explicit(message, category, filename, lineno[, module[, registry[, module_globals]]]) 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). .. versionchanged:: 2.5 Added the *module_globals* parameter. .. function:: warnpy3k(message[, category[, stacklevel]]) Issue a warning related to Python 3.x deprecation. Warnings are only shown when Python is started with the -3 option. Like :func:`warn` *message* must be a string and *category* a subclass of :exc:`Warning`. :func:`warnpy3k` is using :exc:`DeprecationWarning` as default warning class. .. versionadded:: 2.6 .. function:: showwarning(message, category, filename, lineno[, file[, line]]) Write a warning to a file. The default implementation calls ``formatwarning(message, category, filename, lineno, line)`` and writes the resulting string to *file*, which defaults to ``sys.stderr``. You may replace this function with an alternative implementation by assigning to ``warnings.showwarning``. *line* is a line of source code to be included in the warning message; if *line* is not supplied, :func:`showwarning` will try to read the line specified by *filename* and *lineno*. .. versionchanged:: 2.7 The *line* argument is required to be supported. .. function:: formatwarning(message, category, filename, lineno[, line]) 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*. .. versionchanged:: 2.6 Added the *line* argument. .. function:: filterwarnings(action[, message[, category[, module[, lineno[, append]]]]]) Insert an entry into the list of :ref:`warnings filter specifications `. 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 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[, lineno[, append]]]) Insert a simple entry into the list of :ref:`warnings filter specifications `. 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. .. 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]) 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 protected. This argument exists primarily for testing the :mod:`warnings` module itself. .. 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. .. note:: In Python 3, the arguments to the constructor for :class:`catch_warnings` are keyword-only arguments. .. versionadded:: 2.6