Add documentation about the default warnings filters.
diff --git a/Doc/library/warnings.rst b/Doc/library/warnings.rst
index 64689ad..720da0f 100644
--- a/Doc/library/warnings.rst
+++ b/Doc/library/warnings.rst
@@ -94,9 +94,6 @@
standard warning categories. A warning category must always be a subclass of
the :exc:`Warning` class.
-.. versionchanged:: 3.2
- :exc:`DeprecationWarning` is ignored by default.
-
.. _warning-filter:
@@ -157,6 +154,27 @@
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`).
+
+* :exc:`ResourceWarning` is ignored unless Python was built in debug mode.
+
+.. versionchanged:: 3.2
+ :exc:`DeprecationWarning` is now ignored by default in addition to
+ :exc:`PendingDeprecationWarning`.
+
+
.. _warning-suppress:
Temporarily Suppressing Warnings