244 lines
8.7 KiB
ReStructuredText
244 lines
8.7 KiB
ReStructuredText
****************************
|
|
What's New In Python 3.2
|
|
****************************
|
|
|
|
: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 3.2, compared to 3.1.
|
|
|
|
|
|
PEP XXX: Stub
|
|
=============
|
|
|
|
|
|
Other Language Changes
|
|
======================
|
|
|
|
Some smaller changes made to the core Python language are:
|
|
|
|
* Stub
|
|
|
|
|
|
New, Improved, and Deprecated Modules
|
|
=====================================
|
|
|
|
* The functools module now includes two new decorators for caching function
|
|
calls, :func:`functools.lru_cache` and :func:`functools.lfu_cache`. These can
|
|
save repeated queries to an external resource whenever the results are
|
|
expected to be the same.
|
|
|
|
For example, adding an LFU decorator to a database query function can save
|
|
database accesses for the most popular searches::
|
|
|
|
@functools.lfu_cache(maxsize=50)
|
|
def get_phone_number(name):
|
|
c = conn.cursor()
|
|
c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,))
|
|
return c.fetchone()[0]
|
|
|
|
The LFU (least-frequently-used) cache gives best results when the distribution
|
|
of popular queries tends to remain the same over time. In contrast, the LRU
|
|
(least-recently-used) cache gives best results when the distribution changes
|
|
over time (for example, the most popular news articles change each day as
|
|
newer articles are added).
|
|
|
|
The two caching decorators can be composed (nested) to handle hybrid cases
|
|
that have both long-term access patterns and some short-term access trends.
|
|
For example, music searches can reflect both long-term patterns (popular
|
|
classics) and short-term trends (new releases)::
|
|
|
|
@functools.lfu_cache(maxsize=500)
|
|
@functools.lru_cache(maxsize=100)
|
|
def find_music(song):
|
|
...
|
|
|
|
(Contributed by Raymond Hettinger)
|
|
|
|
* The previously deprecated :func:`contextlib.nested` function has been
|
|
removed in favor of a plain :keyword:`with` statement which can
|
|
accept multiple context managers. The latter technique is faster
|
|
(because it is built-in), and it does a better job finalizing multiple
|
|
context managers when one of them raises an exception.
|
|
|
|
(Contributed by Georg Brandl and Mattias Brändström;
|
|
`appspot issue 53094 <http://codereview.appspot.com/53094>`_.)
|
|
|
|
* The :class:`ftplib.FTP` class now supports the context manager protocol
|
|
(Contributed by Tarek Ziadé and Giampaolo Rodolà; :issue:`4972`.)
|
|
|
|
* The :func:`shutil.copytree` function has two new options:
|
|
|
|
* *ignore_dangling_symlinks*: when ``symlinks=False`` (meaning that the
|
|
function copies the file pointed to by the symlink, not the symlink
|
|
itself) this option will silence the error thrown if the file doesn't
|
|
exist.
|
|
|
|
* *copy_function*: a callable that will be used to copy files.
|
|
:func:`shutil.copy2` is used by default.
|
|
|
|
(Contributed by Tarek Ziadé.)
|
|
|
|
* The *sqlite3* module has some new features:
|
|
|
|
* XXX *enable_load_extension*
|
|
|
|
* XXX *load_extension*
|
|
|
|
* New :class:`~sqlite3.Connection` attribute
|
|
:attr:`~sqlite3.Connection.in_transaction` is :const:`True` when there
|
|
are uncommitted changes, and :const:`False` otherwise. (Contributed
|
|
by R. David Murray and Shashwat Anand, :issue:`8845`.)
|
|
|
|
* The :mod:`ssl` module has a new class, :class:`~ssl.SSLContext` which
|
|
serves as a container for various persistent SSL data, such as protocol
|
|
settings, certificates, private keys, and various other options.
|
|
The :meth:`~ssl.SSLContext.wrap_socket` method allows to create an
|
|
SSL socket from such an SSL context.
|
|
(Added by Antoine Pitrou; :issue:`8550`.)
|
|
|
|
The :func:`ssl.wrap_socket` constructor function now takes a
|
|
*ciphers* argument that's a string listing the encryption algorithms
|
|
to be allowed; the format of the string is described
|
|
`in the OpenSSL documentation
|
|
<http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT>`__.
|
|
(Added by Antoine Pitrou; :issue:`8322`.)
|
|
|
|
Various options have been added to the :mod:`ssl` module, such as
|
|
:data:`~ssl.OP_NO_SSLv2` which allows to force disabling of the insecure
|
|
and obsolete SSLv2 protocol.
|
|
(Added by Antoine Pitrou; :issue:`4870`.)
|
|
|
|
Another change makes the extension load all of OpenSSL's ciphers and
|
|
digest algorithms so that they're all available. Some SSL
|
|
certificates couldn't be verified, reporting an "unknown algorithm"
|
|
error. (Reported by Beda Kosata, and fixed by Antoine Pitrou;
|
|
:issue:`8484`.)
|
|
|
|
The version of OpenSSL being used is now available as the module
|
|
attributes :data:`ssl.OPENSSL_VERSION` (a string),
|
|
:data:`ssl.OPENSSL_VERSION_INFO` (a 5-tuple), and
|
|
:data:`ssl.OPENSSL_VERSION_NUMBER` (an integer). (Added by Antoine
|
|
Pitrou; :issue:`8321`.)
|
|
|
|
* The previously deprecated :func:`string.maketrans` function has been
|
|
removed in favor of the static methods, :meth:`bytes.maketrans` and
|
|
:meth:`bytearray.maketrans`. This change solves the confusion around which
|
|
types were supported by the :mod:`string` module. Now, :class:`str`,
|
|
:class:`bytes`, and :class:`bytearray` each have their own **maketrans** and
|
|
**translate** methods with intermediate translation tables of the
|
|
appropriate type.
|
|
|
|
(Contributed by Georg Brandl; :issue:`5675`.)
|
|
|
|
|
|
Multi-threading
|
|
===============
|
|
|
|
* The mechanism for serializing execution of concurrently running Python
|
|
threads (generally known as the GIL or Global Interpreter Lock) has been
|
|
rewritten. Among the objectives were more predictable switching intervals
|
|
and reduced overhead due to lock contention and the number of ensuing
|
|
system calls. The notion of a "check interval" to allow thread switches
|
|
has been abandoned and replaced by an absolute duration expressed in
|
|
seconds. This parameter is tunable through :func:`sys.setswitchinterval()`.
|
|
It currently defaults to 5 milliseconds.
|
|
|
|
Additional details about the implementation can be read from a `python-dev
|
|
mailing-list message
|
|
<http://mail.python.org/pipermail/python-dev/2009-October/093321.html>`_
|
|
(however, "priority requests" as exposed in this message have not been
|
|
kept for inclusion).
|
|
|
|
(Contributed by Antoine Pitrou.)
|
|
|
|
* Recursive locks (created with the :func:`threading.RLock` API) now benefit
|
|
from a C implementation which makes them as fast as regular locks, and
|
|
between 10x and 15x faster than their previous pure Python implementation.
|
|
|
|
(Contributed by Antoine Pitrou; :issue:`3001`.)
|
|
|
|
* Regular and recursive locks now accept an optional *timeout* argument
|
|
to their ``acquire`` method. (Contributed by Antoine Pitrou; :issue:`7316`)
|
|
Similarly, :meth:`threading.Semaphore.acquire` also gains a *timeout*
|
|
argument. (Contributed by Torsten Landschoff; :issue:`850728`.)
|
|
|
|
|
|
Optimizations
|
|
=============
|
|
|
|
Major performance enhancements have been added:
|
|
|
|
* Stub
|
|
|
|
IDLE
|
|
====
|
|
|
|
* Stub
|
|
|
|
|
|
Build and C API Changes
|
|
=======================
|
|
|
|
Changes to Python's build process and to the C API include:
|
|
|
|
* Stub
|
|
|
|
|
|
Porting to Python 3.2
|
|
=====================
|
|
|
|
This section lists previously described changes and other bugfixes
|
|
that may require changes to your code:
|
|
|
|
* bytearray objects cannot be used anymore as filenames: convert them to bytes
|
|
|
|
* PyArg_Parse*() functions:
|
|
|
|
* "t#" format has been removed: use "s#" or "s*" instead
|
|
* "w" and "w#" formats has been removed: use "w*" instead
|
|
|