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diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst new file mode 100644 index 0000000000..eb62968606 --- /dev/null +++ b/Doc/whatsnew/3.3.rst @@ -0,0 +1,543 @@ +**************************** + What's New In Python 3.3 +**************************** + +:Author: Raymond Hettinger +:Release: |release| +:Date: |today| + +.. 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: + + XXX Describe the transmogrify() function added to the socket + module. + (Contributed by P.Y. Developer in :issue:`12345`.) + + This saves the maintainer the effort of going through the Mercurial log + when researching a change. + +This article explains the new features in Python 3.3, compared to 3.2. + + +PEP 393: Flexible String Representation +======================================= + +[Abstract copied from the PEP: The Unicode string type is changed to support +multiple internal representations, depending on the character with the largest +Unicode ordinal (1, 2, or 4 bytes). This allows a space-efficient +representation in common cases, but gives access to full UCS-4 on all systems. +For compatibility with existing APIs, several representations may exist in +parallel; over time, this compatibility should be phased out.] + +PEP 393 is fully backward compatible. The legacy API should remain +available at least five years. Applications using the legacy API will not +fully benefit of the memory reduction, or worse may use a little bit more +memory, because Python may have to maintain two versions of each string (in +the legacy format and in the new efficient storage). + +XXX Add list of changes introduced by :pep:`393` here: + +* Python now always supports the full range of Unicode codepoints, including + non-BMP ones (i.e. from ``U+0000`` to ``U+10FFFF``). The distinction between + narrow and wide builds no longer exists and Python now behaves like a wide + build. + +* The storage of Unicode strings now depends on the highest codepoint in the string: + + * pure ASCII and Latin1 strings (``U+0000-U+00FF``) use 1 byte per codepoint; + + * BMP strings (``U+0000-U+FFFF``) use 2 bytes per codepoint; + + * non-BMP strings (``U+10000-U+10FFFF``) use 4 bytes per codepoint. + +.. The memory usage of Python 3.3 is two to three times smaller than Python 3.2, + and a little bit better than Python 2.7, on a `Django benchmark + <http://mail.python.org/pipermail/python-dev/2011-September/113714.html>`_. + XXX The result should be moved in the PEP and a small summary about + performances and a link to the PEP should be added here. + +* Some of the problems visible on narrow builds have been fixed, for example: + + * :func:`len` now always returns 1 for non-BMP characters, + so ``len('\U0010FFFF') == 1``; + + * surrogate pairs are not recombined in string literals, + so ``'\uDBFF\uDFFF' != '\U0010FFFF'``; + + * indexing or slicing a non-BMP characters doesn't return surrogates anymore, + so ``'\U0010FFFF'[0]`` now returns ``'\U0010FFFF'`` and not ``'\uDBFF'``; + + * several other functions in the stdlib now handle correctly non-BMP codepoints. + +* The value of :data:`sys.maxunicode` is now always ``1114111`` (``0x10FFFF`` + in hexadecimal). The :c:func:`PyUnicode_GetMax` function still returns + either ``0xFFFF`` or ``0x10FFFF`` for backward compatibility, and it should + not be used with the new Unicode API (see :issue:`13054`). + +* The :file:`./configure` flag ``--with-wide-unicode`` has been removed. + +XXX mention new and deprecated functions and macros + + +PEP 3151: Reworking the OS and IO exception hierarchy +===================================================== + +:pep:`3151` - Reworking the OS and IO exception hierarchy +PEP written and implemented by Antoine Pitrou. + +New subclasses of :exc:`OSError` exceptions: + + * :exc:`BlockingIOError` + * :exc:`ChildProcessError` + * :exc:`ConnectionError` + + * :exc:`BrokenPipeError` + * :exc:`ConnectionAbortedError` + * :exc:`ConnectionRefusedError` + * :exc:`ConnectionResetError` + + * :exc:`FileExistsError` + * :exc:`FileNotFoundError` + * :exc:`InterruptedError` + * :exc:`IsADirectoryError` + * :exc:`NotADirectoryError` + * :exc:`PermissionError` + * :exc:`ProcessLookupError` + * :exc:`TimeoutError` + +The following exceptions have been merged into :exc:`OSError`: + + * :exc:`EnvironmentError` + * :exc:`IOError` + * :exc:`WindowsError` + * :exc:`VMSError` + * :exc:`socket.error` + * :exc:`select.error` + * :exc:`mmap.error` + +Thanks to the new exceptions, common usages of the :mod:`errno` can now be +avoided. For example, the following code written for Python 3.2: :: + + from errno import ENOENT, EACCES, EPERM + + try: + with open("document.txt") as f: + content = f.read() + except IOError as err: + if err.errno == ENOENT: + print("document.txt file is missing") + elif err.errno in (EACCES, EPERM): + print("You are not allowed to read document.txt") + else: + raise + +can now be written without the :mod:`errno` import: :: + + try: + with open("document.txt") as f: + content = f.read() + except FileNotFoundError: + print("document.txt file is missing") + except PermissionError: + print("You are not allowed to read document.txt") + + +Other Language Changes +====================== + +Some smaller changes made to the core Python language are: + +* Stub + + +New, Improved, and Deprecated Modules +===================================== + +* Stub + +array +----- + +The :mod:`array` module supports the :c:type:`long long` type using ``q`` and +``Q`` type codes. + +(Contributed by Oren Tirosh and Hirokazu Yamamoto in :issue:`1172711`) + + +codecs +------ + +The :mod:`~encodings.mbcs` codec has be rewritten to handle correclty +``replace`` and ``ignore`` error handlers on all Windows versions. The +:mod:`~encodings.mbcs` codec is now supporting all error handlers, instead of +only ``replace`` to encode and ``ignore`` to decode. + +Multibyte CJK decoders now resynchronize faster. They only ignore the first +byte of an invalid byte sequence. For example, ``b'\xff\n'.decode('gb2312', +'replace')`` now returns a ``\n`` after the replacement character. + +(:issue:`12016`) + +Don't reset incremental encoders of CJK codecs at each call to their encode() +method anymore. For example:: + + $ ./python -q + >>> import codecs + >>> encoder = codecs.getincrementalencoder('hz')('strict') + >>> b''.join(encoder.encode(x) for x in '\u52ff\u65bd\u65bc\u4eba\u3002 Bye.') + b'~{NpJ)l6HK!#~} Bye.' + +This example gives ``b'~{Np~}~{J)~}~{l6~}~{HK~}~{!#~} Bye.'`` with older Python +versions. + +(:issue:`12100`) + +crypt +----- + +Addition of salt and modular crypt format and the :func:`~crypt.mksalt` +function to the :mod:`crypt` module. + +(:issue:`10924`) + +curses +------ + + * The :class:`curses.window` class has a new :meth:`~curses.window.get_wch` + method to get a wide character + * The :mod:`curses` module has a new :meth:`~curses.unget_wch` function to + push a wide character so the next :meth:`~curses.window.get_wch` will return + it + +(Contributed by Iñigo Serna in :issue:`6755`) + +faulthandler +------------ + +New module: :mod:`faulthandler`. + + * :envvar:`PYTHONFAULTHANDLER` + * :option:`-X` ``faulthandler`` + + +ftplib +------ + +The :class:`~ftplib.FTP_TLS` class now provides a new +:func:`~ftplib.FTP_TLS.ccc` function to revert control channel back to +plaintex. This can be useful to take advantage of firewalls that know how to +handle NAT with non-secure FTP without opening fixed ports. + +(Contributed by Giampaolo Rodolà in :issue:`12139`) + + +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 NNTP('news.gmane.org') as n: + ... n.group('gmane.comp.python.committers') + ... + ('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, '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`.) + +* "at" functions (:issue:`4761`): + + * :func:`~os.faccessat` + * :func:`~os.fchmodat` + * :func:`~os.fchownat` + * :func:`~os.fstatat` + * :func:`~os.futimesat` + * :func:`~os.futimesat` + * :func:`~os.linkat` + * :func:`~os.mkdirat` + * :func:`~os.mkfifoat` + * :func:`~os.mknodat` + * :func:`~os.openat` + * :func:`~os.readlinkat` + * :func:`~os.renameat` + * :func:`~os.symlinkat` + * :func:`~os.unlinkat` + * :func:`~os.utimensat` + * :func:`~os.utimensat` + +* extended attributes (:issue:`12720`): + + * :func:`~os.fgetxattr` + * :func:`~os.flistxattr` + * :func:`~os.fremovexattr` + * :func:`~os.fsetxattr` + * :func:`~os.getxattr` + * :func:`~os.lgetxattr` + * :func:`~os.listxattr` + * :func:`~os.llistxattr` + * :func:`~os.lremovexattr` + * :func:`~os.lsetxattr` + * :func:`~os.removexattr` + * :func:`~os.setxattr` + +* Scheduler functions (:issue:`12655`): + + * :func:`~os.sched_get_priority_max` + * :func:`~os.sched_get_priority_min` + * :func:`~os.sched_getaffinity` + * :func:`~os.sched_getparam` + * :func:`~os.sched_getscheduler` + * :func:`~os.sched_rr_get_interval` + * :func:`~os.sched_setaffinity` + * :func:`~os.sched_setparam` + * :func:`~os.sched_setscheduler` + * :func:`~os.sched_yield` + +* Add some extra posix functions to the os module (:issue:`10812`): + + * :func:`~os.fexecve` + * :func:`~os.futimens` + * :func:`~os.futimens` + * :func:`~os.futimes` + * :func:`~os.futimes` + * :func:`~os.lockf` + * :func:`~os.lutimes` + * :func:`~os.lutimes` + * :func:`~os.posix_fadvise` + * :func:`~os.posix_fallocate` + * :func:`~os.pread` + * :func:`~os.pwrite` + * :func:`~os.readv` + * :func:`~os.sync` + * :func:`~os.truncate` + * :func:`~os.waitid` + * :func:`~os.writev` + +* Other new functions: + + * :func:`~os.fdlistdir` (:issue:`10755`) + * :func:`~os.getgrouplist` (:issue:`9344`) + + +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 :data:`~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. + * :func:`~signal.sigwaitinfo`: wait for a signal, returning detailed + information about it. + * :func:`~signal.sigtimedwait`: like :func:`~signal.sigwaitinfo` but with a + timeout. + +* 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. + +socket +------ + +* The :class:`~socket.socket` class now exposes additional methods to process + ancillary data when supported by the underlying platform: + + * :func:`~socket.socket.sendmsg` + * :func:`~socket.socket.recvmsg` + * :func:`~socket.socket.recvmsg_into` + + (Contributed by David Watson in :issue:`6560`, based on an earlier patch by + Heiko Wundram) + +* The :class:`~socket.socket` class now supports the PF_CAN protocol family + (http://en.wikipedia.org/wiki/Socketcan), on Linux + (http://lwn.net/Articles/253425). + + (Contributed by Matthias Fuchs, updated by Tiago Gonçalves in :issue:`10141`) + + +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. + + +shutil +------ + +* The :mod:`shutil` module has these new fuctions: + + * :func:`~shutil.disk_usage`: provides total, used and free disk space + statistics. (Contributed by Giampaolo Rodolà in :issue:`12442`) + * :func:`~shutil.chown`: allows one to change user and/or group of the given + path also specifying the user/group names and not only their numeric + ids. (Contributed by Sandro Tosi in :issue:`12191`) + +urllib +------ + +The :class:`~urllib.request.Request` class, now accepts a *method* argument +used by :meth:`~urllib.request.Request.get_method` to determine what HTTP method +should be used. For example, this will send an ``'HEAD'`` request:: + + >>> urlopen(Request('http://www.python.org', method='HEAD')) + +(:issue:`1673007`) + +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: + +* Issue #12326: On Linux, sys.platform doesn't contain the major version + anymore. It is now always 'linux', instead of 'linux2' or 'linux3' depending + on the Linux version used to build Python. Replace sys.platform == 'linux2' + with sys.platform.startswith('linux'), or directly sys.platform == 'linux' if + you don't need to support older Python versions. + +.. 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. + +* :pep:`393`: The :c:type:`Py_UNICODE` type and all functions using this type + are deprecated. To fully benefit of the memory footprint reduction provided + by the PEP 393, you have to convert your code to the new Unicode API. Read + the porting guide: XXX. + |