* :ref:`pip should always be "available" <whatsnew-pep-453>` (:pep:`453`).
* :ref:`Make newly created file descriptors non-inheritable <whatsnew-pep-446>`
(:pep:`446`).
-* command line option for :ref:`isolated mode <using-on-misc-options>`,
+* command line option for :ref:`isolated mode <whatsnew-isolated-mode>`,
(:issue:`16499`).
* :ref:`improvements in the handling of codecs <codec-handling-improvements>`
that are not text encodings (multiple issues).
method for its *base* argument. (Contributed by Mark Dickinson in
:issue:`16772`.)
+* Frame objects now have a :func:`~frame.clear` method that clears all
+ references to local variables from the frame. (Contributed by Antoine Pitrou
+ in :issue:`17934`.)
+
New Modules
===========
A new :func:`traceback.clear_frames` function takes a traceback object
and clears the local variables in all of the frames it references,
-reducing the amount of memory consumed (:issue:`1565525`).
+reducing the amount of memory consumed. (Contributed by Andrew Kuchling in
+:issue:`1565525`).
urllib
Other Improvements
------------------
+.. _whatsnew-isolated-mode:
+
+* The :ref:`python <using-on-cmdline>` command has a new :ref:`option
+ <using-on-misc-options>`, ``-I``, which causes it to run in "isolated mode",
+ which means that :data:`sys.path` contains neither the script's directory nor
+ the user's ``site-packages`` directory, and all :envvar:`PYTHON*` environment
+ variables are ignored (it implies both ``-s`` and ``-E``). Other
+ restrictions may also be applied in the future, with the goal being to
+ isolate the execution of a script from the user's environment. This is
+ appropriate, for example, when Python is used to run a system script. On
+ most POSIX systems it can and should be used in the ``#!`` line of system
+ scripts. (Contributed by Christian Heims in :issue:`16499`.)
+
* Tab-completion is now enabled by default in the interactive interpreter.
(Contributed by Antoine Pitrou and Éric Araujo in :issue:`5845`.)