mirror of https://github.com/python/cpython
262 lines
9.3 KiB
ReStructuredText
262 lines
9.3 KiB
ReStructuredText
****************************
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What's New In Python 3.2
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****************************
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:Author: Raymond Hettinger
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:Release: |release|
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:Date: |today|
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.. $Id$
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Rules for maintenance:
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* Anyone can add text to this document. Do not spend very much time
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on the wording of your changes, because your text will probably
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get rewritten to some degree.
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* The maintainer will go through Misc/NEWS periodically and add
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changes; it's therefore more important to add your changes to
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Misc/NEWS than to this file.
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* This is not a complete list of every single change; completeness
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is the purpose of Misc/NEWS. Some changes I consider too small
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or esoteric to include. If such a change is added to the text,
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I'll just remove it. (This is another reason you shouldn't spend
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too much time on writing your addition.)
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* If you want to draw your new text to the attention of the
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maintainer, add 'XXX' to the beginning of the paragraph or
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section.
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* It's OK to just add a fragmentary note about a change. For
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example: "XXX Describe the transmogrify() function added to the
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socket module." The maintainer will research the change and
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write the necessary text.
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* You can comment out your additions if you like, but it's not
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necessary (especially when a final release is some months away).
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* Credit the author of a patch or bugfix. Just the name is
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sufficient; the e-mail address isn't necessary.
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* It's helpful to add the bug/patch number as a comment:
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% Patch 12345
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XXX Describe the transmogrify() function added to the socket
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module.
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(Contributed by P.Y. Developer.)
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This saves the maintainer the effort of going through the SVN log
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when researching a change.
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This article explains the new features in Python 3.2, compared to 3.1.
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PEP XXX: Stub
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=============
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Other Language Changes
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======================
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Some smaller changes made to the core Python language are:
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* Stub
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New, Improved, and Deprecated Modules
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=====================================
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* The functools module now includes a new decorator for caching function calls.
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:func:`functools.lru_cache` can save repeated queries to an external resource
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whenever the results are expected to be the same.
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For example, adding a caching decorator to a database query function can save
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database accesses for popular searches::
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@functools.lru_cache(maxsize=300)
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def get_phone_number(name):
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c = conn.cursor()
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c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,))
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return c.fetchone()[0]
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To help with choosing an effective cache size, the wrapped function is
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instrumented with two attributes *hits* and *misses*::
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>>> for name in user_requests:
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... get_phone_number(name)
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>>> print(get_phone_number.hits, get_phone_number.misses)
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4805 980
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If the phonelist table gets updated, the outdated contents of the cache can be
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cleared with::
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>>> get_phone_number.clear()
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(Contributed by Raymond Hettinger)
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* The previously deprecated :func:`contextlib.nested` function has been
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removed in favor of a plain :keyword:`with` statement which can
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accept multiple context managers. The latter technique is faster
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(because it is built-in), and it does a better job finalizing multiple
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context managers when one of them raises an exception.
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(Contributed by Georg Brandl and Mattias Brändström;
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`appspot issue 53094 <http://codereview.appspot.com/53094>`_.)
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* The :class:`ftplib.FTP` class now supports the context manager protocol
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(Contributed by Tarek Ziadé and Giampaolo Rodolà; :issue:`4972`.)
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* A warning message will now get printed at interpreter shutdown if
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the :data:`gc.garbage` list isn't empty. This is meant to make the
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programmer aware that his code contains object finalization issues.
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(Added by Antoine Pitrou; :issue:`477863`.)
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* The :func:`shutil.copytree` function has two new options:
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* *ignore_dangling_symlinks*: when ``symlinks=False`` (meaning that the
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function copies the file pointed to by the symlink, not the symlink
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itself) this option will silence the error raised if the file doesn't
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exist.
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* *copy_function*: a callable that will be used to copy files.
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:func:`shutil.copy2` is used by default.
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(Contributed by Tarek Ziadé.)
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* Socket objects now have a :meth:`~socket.socket.detach()` method which
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puts the socket into closed state without actually closing the underlying
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file descriptor. The latter can then be reused for other purposes.
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(Added by Antoine Pitrou; :issue:`8524`.)
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* The *sqlite3* module has some new features:
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* XXX *enable_load_extension*
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* XXX *load_extension*
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* New :class:`~sqlite3.Connection` attribute
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:attr:`~sqlite3.Connection.in_transaction` is :const:`True` when there
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are uncommitted changes, and :const:`False` otherwise. (Contributed
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by R. David Murray and Shashwat Anand, :issue:`8845`.)
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* The :mod:`ssl` module has a new class, :class:`~ssl.SSLContext` which
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serves as a container for various persistent SSL data, such as protocol
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settings, certificates, private keys, and various other options.
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The :meth:`~ssl.SSLContext.wrap_socket` method allows to create an
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SSL socket from such an SSL context.
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(Added by Antoine Pitrou; :issue:`8550`.)
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The :func:`ssl.wrap_socket` constructor function now takes a
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*ciphers* argument that's a string listing the encryption algorithms
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to be allowed; the format of the string is described
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`in the OpenSSL documentation
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<http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT>`__.
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(Added by Antoine Pitrou; :issue:`8322`.)
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Various options have been added to the :mod:`ssl` module, such as
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:data:`~ssl.OP_NO_SSLv2` which allows to force disabling of the insecure
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and obsolete SSLv2 protocol.
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(Added by Antoine Pitrou; :issue:`4870`.)
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Another change makes the extension load all of OpenSSL's ciphers and
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digest algorithms so that they're all available. Some SSL
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certificates couldn't be verified, reporting an "unknown algorithm"
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error. (Reported by Beda Kosata, and fixed by Antoine Pitrou;
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:issue:`8484`.)
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The version of OpenSSL being used is now available as the module
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attributes :data:`ssl.OPENSSL_VERSION` (a string),
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:data:`ssl.OPENSSL_VERSION_INFO` (a 5-tuple), and
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:data:`ssl.OPENSSL_VERSION_NUMBER` (an integer). (Added by Antoine
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Pitrou; :issue:`8321`.)
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* The previously deprecated :func:`string.maketrans` function has been
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removed in favor of the static methods, :meth:`bytes.maketrans` and
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:meth:`bytearray.maketrans`. This change solves the confusion around which
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types were supported by the :mod:`string` module. Now, :class:`str`,
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:class:`bytes`, and :class:`bytearray` each have their own **maketrans** and
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**translate** methods with intermediate translation tables of the
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appropriate type.
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(Contributed by Georg Brandl; :issue:`5675`.)
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* Parameters passed to :func:`socket.getaddrinfo()` function can now be
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specified as single keyword arguments.
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(Contributed by Giampaolo Rodolà; :issue:`8866`.)
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* :class:`~poplib.POP3_SSL` class now accepts a *context* parameter, which is a
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:class:`ssl.SSLContext` object allowing bundling SSL configuration options,
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certificates and private keys into a single (potentially long-lived)
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structure.
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(Contributed by Giampaolo Rodolà; :issue:`8807`.)
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Multi-threading
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===============
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* The mechanism for serializing execution of concurrently running Python
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threads (generally known as the GIL or Global Interpreter Lock) has been
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rewritten. Among the objectives were more predictable switching intervals
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and reduced overhead due to lock contention and the number of ensuing
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system calls. The notion of a "check interval" to allow thread switches
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has been abandoned and replaced by an absolute duration expressed in
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seconds. This parameter is tunable through :func:`sys.setswitchinterval()`.
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It currently defaults to 5 milliseconds.
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Additional details about the implementation can be read from a `python-dev
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mailing-list message
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<http://mail.python.org/pipermail/python-dev/2009-October/093321.html>`_
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(however, "priority requests" as exposed in this message have not been
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kept for inclusion).
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(Contributed by Antoine Pitrou.)
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* Recursive locks (created with the :func:`threading.RLock` API) now benefit
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from a C implementation which makes them as fast as regular locks, and
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between 10x and 15x faster than their previous pure Python implementation.
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(Contributed by Antoine Pitrou; :issue:`3001`.)
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* Regular and recursive locks now accept an optional *timeout* argument
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to their ``acquire`` method. (Contributed by Antoine Pitrou; :issue:`7316`)
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Similarly, :meth:`threading.Semaphore.acquire` also gains a *timeout*
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argument. (Contributed by Torsten Landschoff; :issue:`850728`.)
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Optimizations
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=============
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Major performance enhancements have been added:
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* Stub
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IDLE
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====
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* Stub
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Build and C API Changes
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=======================
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Changes to Python's build process and to the C API include:
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* Stub
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Porting to Python 3.2
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=====================
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This section lists previously described changes and other bugfixes
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that may require changes to your code:
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* bytearray objects cannot be used anymore as filenames: convert them to bytes
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* PyArg_Parse*() functions:
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* "t#" format has been removed: use "s#" or "s*" instead
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* "w" and "w#" formats has been removed: use "w*" instead
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