DeprecationWarning is now silent by default.
This was originally suggested by Guido, discussed on the stdlib-sig mailing
list, and given the OK by Guido directly to me. What this change essentially
means is that Python has taken a policy of silencing warnings that are only
of interest to developers by default. This should prevent users from seeing
warnings which are triggered by an application being run against a new
interpreter before the app developer has a chance to update their code.
Closes issue #7319. Thanks to Antoine Pitrou, Ezio Melotti, and Brian Curtin
for helping with the issue.
diff --git a/Doc/library/warnings.rst b/Doc/library/warnings.rst
index b018a33..e4343e8 100644
--- a/Doc/library/warnings.rst
+++ b/Doc/library/warnings.rst
@@ -59,7 +59,7 @@
| :exc:`UserWarning` | The default category for :func:`warn`. |
+----------------------------------+-----------------------------------------------+
| :exc:`DeprecationWarning` | Base category for warnings about deprecated |
-| | features. |
+| | features (ignored by default). |
+----------------------------------+-----------------------------------------------+
| :exc:`SyntaxWarning` | Base category for warnings about dubious |
| | syntactic features. |
@@ -89,6 +89,9 @@
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:
@@ -148,14 +151,6 @@
:mod:`warnings` module parses these when it is first imported (invalid options
are ignored, after printing a message to ``sys.stderr``).
-The warnings that are ignored by default may be enabled by passing :option:`-Wd`
-to the interpreter. This enables default handling for all warnings, including
-those that are normally ignored by default. This is particular useful for
-enabling ImportWarning when debugging problems importing a developed package.
-ImportWarning can also be enabled explicitly in Python code using::
-
- warnings.simplefilter('default', ImportWarning)
-
.. _warning-suppress:
@@ -226,6 +221,37 @@
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`
+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