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diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst new file mode 100644 index 0000000..d56b422 --- /dev/null +++ b/Doc/whatsnew/3.4.rst @@ -0,0 +1,498 @@ +**************************** + What's New In Python 3.4 +**************************** + +.. :Author: Someone <email> + (uncomment if there is a principal author) + +.. Rules for maintenance: + + * Anyone can add text to this document, but the maintainer reserves the + right to rewrite any additions. In particular, for obscure or esoteric + features, the maintainer may reduce any addition to a simple reference to + the new documentation rather than explaining the feature inline. + + * While the maintainer will periodically go through Misc/NEWS + and add changes, it's best not to rely on this. We know from experience + that any changes that aren't in the What's New documentation around the + time of the original release will remain largely unknown to the community + for years, even if they're added later. We also know from experience that + other priorities can arise, and the maintainer will run out of time to do + updates - in such cases, end users will be much better served by partial + notifications that at least give a hint about new features to + investigate. + + * This is not a complete list of every single change; completeness + is the purpose of Misc/NEWS. The What's New should focus on changes that + are visible to Python *users* and that *require* a feature release (i.e. + most bug fixes should only be recorded in Misc/NEWS) + + * PEPs should not be marked Final until they have an entry in What's New. + A placeholder entry that is just a section header and a link to the PEP + (e.g ":pep:`397` has been implemented") is acceptable. If a PEP has been + implemented and noted in What's New, don't forget to mark it as Final! + + * 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 add just a very brief note about a change. For + example: "The :ref:`~socket.transmogrify()` function was added to the + :mod:`socket` module." The maintainer will research the change and + write the necessary text (if appropriate). The advantage of doing this + is that even if no more descriptive text is ever added, readers will at + least have a notification that the new feature exists and a link to the + relevant documentation. + + * 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: + + The :ref:`~socket.transmogrify()` function was added to the + :mod:`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. + + * Cross referencing tip: :ref:`mod.attr` will display as ``mod.attr``, + while :ref:`~mod.attr` will display as ``attr``. + +This article explains the new features in Python 3.4, compared to 3.3. + +.. Python 3.4 was released on TBD. + +For full details, see the +`changelog <http://docs.python.org/3.4/whatsnew/changelog.html>`_. + +.. note:: Prerelease users should be aware that this document is currently in + draft form. It will be updated substantially as Python 3.4 moves towards + release, so it's worth checking back even after reading earlier versions. + + +.. seealso:: + + .. :pep:`4XX` - Python 3.4 Release Schedule + + +Summary -- Release highlights +============================= + +.. This section singles out the most important changes in Python 3.4. + Brevity is key. + +New syntax features: + +* None yet. + +New library modules: + +* :mod:`enum`: Implementation of the :pep:`435`. + +New built-in features: + +* :ref:`PEP 442: Safe object finalization <pep-442>`. +* :ref:`PEP 445: Configurable memory allocators <pep-445>`. + +Implementation improvements: + +* A more efficient :mod:`marshal` format (:issue:`16475`). +* Improve finalization of Python modules to avoid setting their globals + to None, in most cases (:issue:`18214`). + +Significantly Improved Library Modules: + +* Single-dispatch generic functions (:pep:`443`) +* SHA-3 (Keccak) support for :mod:`hashlib`. +* TLSv1.1 and TLSv1.2 support for :mod:`ssl`. +* :mod:`multiprocessing` now has option to avoid using :func:`os.fork` + on Unix (:issue:`8713`). + +Security improvements: + +* command line option for :ref:`isolated mode <using-on-misc-options>`, + :issue:`16499`. + +Please read on for a comprehensive list of user-facing changes. + +.. _pep-445: + +PEP 445: Add new APIs to customize Python memory allocators +=========================================================== + +The :pep:`445` adds new Application Programming Interfaces (API) to customize +Python memory allocators. + + +.. _pep-442: + +PEP 442: Safe object finalization +================================= + +This PEP removes the current limitations and quirks of object finalization. +With it, objects with :meth:`__del__` methods, as well as generators +with :keyword:`finally` clauses, can be finalized when they are part of a +reference cycle. + +.. seealso:: + + :pep:`442` - Safe object finalization + PEP written and implemented by Antoine Pitrou + + +Other Language Changes +====================== + +Some smaller changes made to the core Python language are: + +* Unicode database updated to UCD version 6.2. + +* :func:`min` and :func:`max` now accept a *default* argument that can be used + to specify the value they return if the iterable they are evaluating has no + elements. Contributed by Julian Berman in :issue:`18111`. + +* Module objects are now :mod:`weakref`'able. + + +New Modules +=========== + +.. module name +.. ----------- + +* None yet. + + +Improved Modules +================ + +aifc +---- + +The :meth:`~aifc.getparams` method now returns a namedtuple rather than a +plain tuple. (Contributed by Claudiu Popa in :issue:`17818`.) + + +colorsys +-------- + +The number of digits in the coefficients for the RGB --- YIQ conversions have +been expanded so that they match the FCC NTSC versions. The change in +results should be less than 1% and may better match results found elsewhere. + + +dis +--- + +The :mod:`dis` module is now built around an :class:`Instruction` class that +provides details of individual bytecode operations and a +:func:`get_instructions` iterator that emits the Instruction stream for a +given piece of Python code. The various display tools in the :mod:`dis` +module have been updated to be based on these new components. + +The new :class:`dis.Bytecode` class provides an object-oriented API for +inspecting bytecode, both in human-readable form and for iterating over +instructions. + +(Contributed by Nick Coghlan, Ryan Kelly and Thomas Kluyver in :issue:`11816`) + + +doctest +------- + +Added :data:`~doctest.FAIL_FAST` flag to halt test running as soon as the first +failure is detected. (Contributed by R. David Murray and Daniel Urban in +:issue:`16522`.) + +Updated the doctest command line interface to use :mod:`argparse`, and added +``-o`` and ``-f`` options to the interface. ``-o`` allows doctest options to +be specified on the command line, and ``-f`` is a shorthand for ``-o +FAIL_FAST`` (to parallel the similar option supported by the :mod:`unittest` +CLI). (Contributed by R. David Murray in :issue:`11390`.) + + +email +----- + +:meth:`~email.message.Message.as_string` now accepts a *policy* argument to +override the default policy of the message when generating a string +representation of it. This means that ``as_string`` can now be used in more +circumstances, instead of having to create and use a :mod:`~email.generator` in +order to pass formatting parameters to its ``flatten`` method. + +New method :meth:`~email.message.Message.as_bytes` added to produce a bytes +representation of the message in a fashion similar to how ``as_string`` +produces a string representation. It does not accept the *maxheaderlen* +argument, but does accept the *unixfrom* and *policy* arguments. The +:class:`~email.message.Message` :meth:`~email.message.Message.__bytes__` method +calls it, meaning that ``bytes(mymsg)`` will now produce the intuitive +result: a bytes object containing the fully formatted message. + +(Contributed by R. David Murray in :issue:`18600`.) + + +functools +--------- + +New :func:`functools.singledispatch` decorator: see the :pep:`443`. + + +inspect +------- + +:func:`~inspect.unwrap` makes it easy to unravel wrapper function chains +created by :func:`functools.wraps` (and any other API that sets the +``__wrapped__`` attribute on a wrapper function). + + +mmap +---- + +mmap objects can now be weakref'ed. + +(Contributed by Valerie Lambert in :issue:`4885`.) + + +multiprocessing +--------------- + +On Unix two new *start methods* have been added for starting processes +using :mod:`multiprocessing`. These make the mixing of processes with +threads more robust. See :issue:`8713`. + +Also, except when using the old *fork* start method, child processes +will no longer inherit unneeded handles/file descriptors from their parents. + + +poplib +------ + +New :meth:`~poplib.POP3.stls` method to switch a clear-text POP3 session into +an encrypted POP3 session. + +New :meth:`~poplib.POP3.capa` method to query the capabilities advertised by the +POP3 server. + +(Contributed by Lorenzo Catucci in :issue:`4473`.) + + +smtplib +------- + +:exc:`~smtplib.SMTPException` is now a subclass of :exc:`OSError`, which allows +both socket level errors and SMTP protocol level errors to be caught in one +try/except statement by code that only cares whether or not an error occurred. +(:issue:`2118`). + + +ssl +--- + +TLSv1.1 and TLSv1.2 support. + +(Contributed by Michele Orrù and Antoine Pitrou in :issue:`16692`) + +* New diagnostic functions :func:`~ssl.get_default_verify_paths`, + :meth:`~ssl.SSLContext.cert_store_stats` and + :meth:`~ssl.SSLContext.get_ca_certs` + +* Add :func:`ssl.enum_cert_store` to retrieve certificates and CRL from Windows' + cert store. + +(Contributed by Christian Heimes in :issue:`18143`, :issue:`18147` and + :issue:`17134`.) + +Support for server-side SNI using the new +:meth:`ssl.SSLContext.set_servername_callback` method. + +(Contributed by Daniel Black in :issue:`8109`.) + + +stat +---- + +The :mod:`stat` module is now backed by a C implementation in :mod:`_stat`. A C +implementation is required as most of the values aren't standardized and +platform-dependent. (Contributed by Christian Heimes in :issue:`11016`.) + +The module supports new file types: door, event port and whiteout. + + +struct +------ + +Streaming struct unpacking using :func:`struct.iter_unpack`. + +(Contributed by Antoine Pitrou in :issue:`17804`.) + + +urllib +------ + +Add support.for ``data:`` URLs in :mod:`urllib.request`. + +(Contributed by Mathias Panzenböck in :issue:`16423`.) + + +unittest +-------- + +Support for easy dynamically-generated subtests using the +:meth:`~unittest.TestCase.subTest` context manager. + +(Contributed by Antoine Pitrou in :issue:`16997`.) + + +wave +---- + +The :meth:`~wave.getparams` method now returns a namedtuple rather than a +plain tuple. (Contributed by Claudiu Popa in :issue:`17487`.) + +:meth:`wave.open` now supports the context manager protocol. (Contributed +by Claudiu Popa in :issue:`17616`.) + + +weakref +------- + +New :class:`~weakref.WeakMethod` class simulates weak references to bound +methods. + +(Contributed by Antoine Pitrou in :issue:`14631`.) + + +xml.etree +--------- + +Add an event-driven parser for non-blocking applications, +:class:`~xml.etree.ElementTree.IncrementalParser`. + +(Contributed by Antoine Pitrou in :issue:`17782`.) + + +Other improvements +================== + +Tab-completion is now enabled by default in the interactive interpreter. + +(Contributed by Antoine Pitrou and Éric Araujo in :issue:`5845`.) + + +Optimizations +============= + +Major performance enhancements have been added: + +* The UTF-32 decoder is now 3x to 4x faster. + +* The cost of hash collisions for sets is now reduced. Each hash table + probe now checks a second key/hash pair for each cache line retrieved. + This exploits cache locality to make collision resolution less expensive. + + (Contributed by Raymond Hettinger in :issue"`18771`.) + + +Build and C API Changes +======================= + +Changes to Python's build process and to the C API include: + +* None yet. + + +Deprecated +========== + +Unsupported Operating Systems +----------------------------- + +* OS/2 +* Windows 2000 + + +Deprecated Python modules, functions and methods +------------------------------------------------ + +* :meth:`difflib.SequenceMatcher.isbjunk` and + :meth:`difflib.SequenceMatcher.isbpopular` were removed: use ``x in sm.bjunk`` and + ``x in sm.bpopular``, where *sm* is a :class:`~difflib.SequenceMatcher` object. + +* :func:`importlib.util.module_for_loader` is pending deprecation. Using + :func:`importlib.util.module_to_load` and + :meth:`importlib.abc.Loader.init_module_attrs` allows subclasses of a loader + to more easily customize module loading. + +* The :mod:`imp` module is pending deprecation. To keep compatibility with + Python 2/3 code bases, the module's removal is currently not scheduled. + + +Deprecated functions and types of the C API +------------------------------------------- + +* None yet. + + +Deprecated features +------------------- + +* None yet. + + +Porting to Python 3.4 +===================== + +This section lists previously described changes and other bugfixes +that may require changes to your code. + +* The ABCs defined in :mod:`importlib.abc` now either raise the appropriate + exception or return a default value instead of raising + :exc:`NotImplementedError` blindly. This will only affect code calling + :func:`super` and falling through all the way to the ABCs. For compatibility, + catch both :exc:`NotImplementedError` or the appropriate exception as needed. + +* The module type now initializes the :attr:`__package__` and :attr:`__loader__` + attributes to ``None`` by default. To determine if these attributes were set + in a backwards-compatible fashion, use e.g. + ``getattr(module, '__loader__', None) is not None``. + +* :meth:`importlib.util.module_for_loader` now sets ``__loader__`` and + ``__package__`` unconditionally to properly support reloading. If this is not + desired then you will need to set these attributes manually. You can use + :func:`importlib.util.module_to_load` for module management. + +* Import now resets relevant attributes (e.g. ``__name__``, ``__loader__``, + ``__package__``, ``__file__``, ``__cached__``) unconditionally when reloading. + +* Frozen packages no longer set ``__path__`` to a list containg the package name + but an empty list instead. Determing if a module is a package should be done + using ``hasattr(module, '__path__')``. + +* :c:func:`PyErr_SetImportError` now sets :exc:`TypeError` when its **msg** + argument is not set. Previously only ``NULL`` was returned with no exception + set. + +* :func:`py_compile.compile` now raises :exc:`FileExistsError` if the file path + it would write to is a symlink or a non-regular file. This is to act as a + warning that import will overwrite those files with a regular file regardless + of what type of file path they were originally. + +* :meth:`importlib.abc.SourceLoader.get_source` no longer raises + :exc:`ImportError` when the source code being loaded triggers a + :exc:`SyntaxError` or :exc:`UnicodeDecodeError`. As :exc:`ImportError` is + meant to be raised only when source code cannot be found but it should, it was + felt to be over-reaching/overloading of that meaning when the source code is + found but improperly structured. If you were catching ImportError before and + wish to continue to ignore syntax or decoding issues, catch all three + exceptions now. + +* :func:`functools.update_wrapper` and :func:`functools.wraps` now correctly + set the ``__wrapped__`` attribute even if the wrapped function had a + wrapped attribute set. This means ``__wrapped__`` attributes now correctly + link a stack of decorated functions rather than every ``__wrapped__`` + attribute in the chain referring to the innermost function. Introspection + libraries that assumed the previous behaviour was intentional can use + :func:`inspect.unwrap` to gain equivalent behaviour. |