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forward port r66386

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Benjamin Peterson 2008-10-16 23:24:44 +00:00
parent d31fdc547b
commit fcf5d639f5
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34
Doc/library/warnings.rst
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@ -165,9 +165,9 @@ ImportWarning can also be enabled explicitly in Python code using::
Temporarily Suppressing Warnings
--------------------------------
If you are using code that you know will raise a warning, such some deprecated
function, but do not want to see the warning, then suppress the warning using
the :class:`catch_warnings` context manager::
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
@ -218,7 +218,15 @@ 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.
results. The :func:`showwarning` function in the module is also restored to
its original value.
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-functions:
@ -314,20 +322,20 @@ Available Context Managers
.. class:: catch_warnings([\*, record=False, module=None])
A context manager that copies and, upon exit, restores the warnings filter.
If the *record* argument is False (the default) the context manager returns
:class:`None`. If *record* is true, a list is returned that is populated
with objects as seen by a custom :func:`showwarning` function (which also
suppresses output to ``sys.stdout``). Each object has attributes with the
same names as the arguments to :func:`showwarning`.
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 arguments exists primarily for testing the :mod:`warnings`
protected. This argument exists primarily for testing the :mod:`warnings`
module itself.
.. versionadded:: 2.6
.. versionchanged:: 3.0
Constructor arguments turned into keyword-only arguments.