cpython/Doc/whatsnew/3.3.rst

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****************************
What's New In Python 3.3
****************************
:Author: Raymond Hettinger
:Release: |release|
:Date: |today|
.. $Id$
Rules for maintenance:
* Anyone can add text to this document. Do not spend very much time
on the wording of your changes, because your text will probably
get rewritten to some degree.
* The maintainer will go through Misc/NEWS periodically and add
changes; it's therefore more important to add your changes to
Misc/NEWS than to this file.
* This is not a complete list of every single change; completeness
is the purpose of Misc/NEWS. Some changes I consider too small
or esoteric to include. If such a change is added to the text,
I'll just remove it. (This is another reason you shouldn't spend
too much time on writing your addition.)
* If you want to draw your new text to the attention of the
maintainer, add 'XXX' to the beginning of the paragraph or
section.
* It's OK to just add a fragmentary note about a change. For
example: "XXX Describe the transmogrify() function added to the
socket module." The maintainer will research the change and
write the necessary text.
* You can comment out your additions if you like, but it's not
necessary (especially when a final release is some months away).
* Credit the author of a patch or bugfix. Just the name is
sufficient; the e-mail address isn't necessary.
* It's helpful to add the bug/patch number as a comment:
% Patch 12345
XXX Describe the transmogrify() function added to the socket
module.
(Contributed by P.Y. Developer.)
This saves the maintainer the effort of going through the SVN log
when researching a change.
This article explains the new features in Python 3.3, compared to 3.2.
PEP XXX: Stub
=============
Other Language Changes
======================
Some smaller changes made to the core Python language are:
* Stub
New, Improved, and Deprecated Modules
=====================================
* Stub
faulthandler
------------
New module: :mod:`faulthandler`.
* :envvar:`PYTHONFAULTHANDLER`
* :option:`-X` ``faulthandler``
math
----
The :mod:`math` module has a new function:
* :func:`~math.log2`: return the base-2 logarithm of *x*
(Written by Mark Dickinson in :issue:`11888`).
nntplib
-------
The :class:`nntplib.NNTP` class now supports the context manager protocol to
unconditionally consume :exc:`socket.error` exceptions and to close the NNTP
connection when done::
>>> from nntplib import NNTP
>>> with nntplib.NNTP('news.gmane.org') as n:
... n.group('gmane.comp.python.committers')
...
('211 1454 1 1454 gmane.comp.python.committers', '1454', '1', '1454', 'gmane.comp.python.committers')
>>>
(Contributed by Giampaolo Rodolà in :issue:`9795`)
os
--
* The :mod:`os` module has a new :func:`~os.pipe2` function that makes it
possible to create a pipe with :data:`~os.O_CLOEXEC` or
:data:`~os.O_NONBLOCK` flags set atomically. This is especially useful to
avoid race conditions in multi-threaded programs.
* The :mod:`os` module has a new :func:`~os.sendfile` function which provides
an efficent "zero-copy" way for copying data from one file (or socket)
descriptor to another. The phrase "zero-copy" refers to the fact that all of
the copying of data between the two descriptors is done entirely by the
kernel, with no copying of data into userspace buffers. :func:`~os.sendfile`
can be used to efficiently copy data from a file on disk to a network socket,
e.g. for downloading a file.
(Patch submitted by Ross Lagerwall and Giampaolo Rodolà in :issue:`10882`.)
* The :mod:`os` module has two new functions: :func:`~os.getpriority` and
:func:`~os.setpriority`. They can be used to get or set process
niceness/priority in a fashion similar to :func:`os.nice` but extended to all
processes instead of just the current one.
(Patch submitted by Giampaolo Rodolà in :issue:`10784`.)
packaging
---------
:mod:`distutils` has undergone additions and refactoring under a new name,
:mod:`packaging`, to allow developers to break backward compatibility.
:mod:`distutils` is still provided in the standard library, but users are
encouraged to transition to :mod:`packaging`. For older versions of Python, a
backport compatible with 2.4+ and 3.1+ will be made available on PyPI under the
name :mod:`distutils2`.
.. TODO add examples and howto to the packaging docs and link to them
pydoc
-----
The Tk GUI and the :func:`~pydoc.serve` function have been removed from the
:mod:`pydoc` module: ``pydoc -g`` and :func:`~pydoc.serve` have been deprecated
in Python 3.2.
sys
---
* The :mod:`sys` module has a new :func:`~sys.thread_info` :term:`struct
sequence` holding informations about the thread implementation.
(:issue:`11223`)
signal
------
* The :mod:`signal` module has new functions:
* :func:`~signal.pthread_sigmask`: fetch and/or change the signal mask of the
calling thread (Contributed by Jean-Paul Calderone in :issue:`8407`) ;
* :func:`~signal.pthread_kill`: send a signal to a thread ;
* :func:`~signal.sigpending`: examine pending functions ;
* :func:`~signal.sigwait`: wait a signal.
* The signal handler writes the signal number as a single byte instead of
a nul byte into the wakeup file descriptor. So it is possible to wait more
than one signal and know which signals were raised.
* :func:`signal.signal` and :func:`signal.siginterrupt` raise an OSError,
instead of a RuntimeError: OSError has an errno attribute.
ssl
---
The :mod:`ssl` module has new functions:
* :func:`~ssl.RAND_bytes`: generate cryptographically strong
pseudo-random bytes.
* :func:`~ssl.RAND_pseudo_bytes`: generate pseudo-random bytes.
Optimizations
=============
Major performance enhancements have been added:
* Stub
Build and C API Changes
=======================
Changes to Python's build process and to the C API include:
* Stub
Unsupported Operating Systems
=============================
OS/2 and VMS are no longer supported due to the lack of a maintainer.
Windows 2000 and Windows platforms which set ``COMSPEC`` to ``command.com``
are no longer supported due to maintenance burden.
Porting to Python 3.3
=====================
This section lists previously described changes and other bugfixes
that may require changes to your code:
* Stub
.. Issue #11591: When :program:`python` was started with :option:`-S`,
``import site`` will not add site-specific paths to the module search
paths. In previous versions, it did. See changeset for doc changes in
various files. Contributed by Carl Meyer with editions by Éric Araujo.
.. Issue #10998: -Q command-line flags are related artifacts have been
removed. Code checking sys.flags.division_warning will need updating.
Contributed by Éric Araujo.