**************************** What's New In Python 3.5 **************************** :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 3.5, compared to 3.4. For full details, see the :source:`Misc/NEWS` file. .. note:: Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.5 moves towards release, so it's worth checking back even after reading earlier versions. .. seealso:: :pep:`478` - Python 3.5 Release Schedule Summary -- Release highlights ============================= .. This section singles out the most important changes in Python 3.3. Brevity is key. New syntax features: * None yet. New library modules: * None yet. New built-in features: * None yet. Implementation improvements: * When the ``LC_TYPE`` locale is the POSIX locale (``C`` locale), :py:data:`sys.stdin` and :py:data:`sys.stdout` are now using the ``surrogateescape`` error handler, instead of the ``strict`` error handler (:issue:`19977`). Significantly Improved Library Modules: * None yet. Security improvements: * None yet. Please read on for a comprehensive list of user-facing changes. .. PEP-sized items next. .. _pep-4XX: .. PEP 4XX: Virtual Environments .. ============================= .. (Implemented by Foo Bar.) .. .. seealso:: :pep:`4XX` - Python Virtual Environments PEP written by Carl Meyer PEP 475: Retry system calls failing with EINTR ---------------------------------------------- :pep:`475` adds support for automatic retry of system calls failing with EINTR: this means that user code doesn't have to deal with EINTR or InterruptedError manually, and should make it more robust against asynchronous signal reception. .. seealso:: :pep:`475` -- Retry system calls failing with EINTR Other Language Changes ====================== Some smaller changes made to the core Python language are: * Added the ``'namereplace'`` error handlers. The ``'backslashreplace'`` error handlers now works with decoding and translating. (Contributed by Serhiy Storchaka in :issue:`19676` and :issue:`22286`.) New Modules =========== .. module name .. ----------- * None yet. Improved Modules ================ argparse -------- * :class:`~argparse.ArgumentParser` now allows to disable :ref:`abbreviated usage ` of long options by setting :ref:`allow_abbrev` to ``False``. (Contributed by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.) cgi --- * :class:`~cgi.FieldStorage` now supports the context management protocol. (Contributed by Berker Peksag in :issue:`20289`.) code ---- * The :func:`code.InteractiveInterpreter.showtraceback` method now prints the full chained traceback, just like the interactive interpreter. (Contributed by Claudiu Popa in :issue:`17442`.) compileall ---------- * :func:`compileall.compile_dir` and :mod:`compileall`'s command-line interface can now do parallel bytecode compilation. (Contributed by Claudiu Popa in :issue:`16104`.) contextlib ---------- * The new :func:`contextlib.redirect_stderr` context manager(similar to :func:`contextlib.redirect_stdout`) makes it easier for utility scripts to handle inflexible APIs that write their output to :data:`sys.stderr` and don't provide any options to redirect it. (Contributed by Berker Peksag in :issue:`22389`.) distutils --------- * The ``build`` and ``build_ext`` commands now accept a ``-j`` option to enable parallel building of extension modules. (Contributed by Antoine Pitrou in :issue:`5309`.) doctest ------- * :func:`doctest.DocTestSuite` returns an empty :class:`unittest.TestSuite` if *module* contains no docstrings instead of raising :exc:`ValueError`. (Contributed by Glenn Jones in :issue:`15916`.) glob ---- * :func:`~glob.iglob` and :func:`~glob.glob` now support recursive search in subdirectories using the "``**``" pattern. (Contributed by Serhiy Storchaka in :issue:`13968`.) imaplib ------- * :class:`IMAP4` now supports the context management protocol. When used in a :keyword:`with` statement, the IMAP4 ``LOGOUT`` command will be called automatically at the end of the block. (Contributed by Tarek Ziadé and Serhiy Storchaka in :issue:`4972`.) imghdr ------ * :func:`~imghdr.what` now recognizes the `OpenEXR `_ format. (Contributed by Martin Vignali and Claudiu Popa in :issue:`20295`.) importlib --------- * :class:`importlib.util.LazyLoader` allows for the lazy loading of modules in applications where startup time is paramount. (Contributed by Brett Cannon in :issue:`17621`.) * :func:`importlib.abc.InspectLoader.source_to_code` is now a static method to make it easier to work with source code in a string. With a module object that you want to initialize you can then use ``exec(code, module.__dict__)`` to execute the code in the module. * :func:`importlib.util.module_from_spec` is now the preferred way to create a new module. Compared to :class:`types.ModuleType`, this new function will set the various import-controlled attributes based on the passed-in spec object. inspect ------- * :class:`inspect.Signature` and :class:`inspect.Parameter` are now picklable and hashable. (Contributed by Yury Selivanov in :issue:`20726` and :issue:`20334`.) * New class method :meth:`inspect.Signature.from_callable`, which makes subclassing of :class:`~inspect.Signature` easier. (Contributed by Yury Selivanov and Eric Snow in :issue:`17373`.) ipaddress --------- * :class:`ipaddress.IPv4Network` and :class:`ipaddress.IPv6Network` now accept an ``(address, netmask)`` tuple argument, so as to easily construct network objects from existing addresses. (Contributed by Peter Moody and Antoine Pitrou in :issue:`16531`.) json ---- * The output of :mod:`json.tool` command line interface is now in the same order as the input. Use the :option:`--sort-keys` option to sort the output of dictionaries alphabetically by key. (Contributed by Berker Peksag in :issue:`21650`.) * JSON decoder now raises :exc:`json.JSONDecodeError` instead of :exc:`ValueError`. (Contributed by Serhiy Storchaka in :issue:`19361`.) os -- * :class:`os.stat_result` now has a :attr:`~os.stat_result.st_file_attributes` attribute on Windows. (Contributed by Ben Hoyt in :issue:`21719`.) re -- * Number of capturing groups in regular expression is no longer limited by 100. (Contributed by Serhiy Storchaka in :issue:`22437`.) * Now unmatched groups are replaced with empty strings in :func:`re.sub` and :func:`re.subn`. (Contributed by Serhiy Storchaka in :issue:`1519638`.) math ---- * :data:`math.inf` and :data:`math.nan` constants added. (Contributed by Mark Dickinson in :issue:`23185`.) shutil ------ * :func:`~shutil.move` now accepts a *copy_function* argument, allowing, for example, :func:`~shutil.copy` to be used instead of the default :func:`~shutil.copy2` if there is a need to ignore metadata. (Contributed by Claudiu Popa in :issue:`19840`.) signal ------ * Different constants of :mod:`signal` module are now enumeration values using the :mod:`enum` module. This allows meaningful names to be printed during debugging, instead of integer “magic numbers”. (Contributed by Giampaolo Rodola' in :issue:`21076`.) smtpd ----- * Both :class:`~smtpd.SMTPServer` and :class:`smtpd.SMTPChannel` now accept a *decode_data* keyword to determine if the DATA portion of the SMTP transaction is decoded using the ``utf-8`` codec or is instead provided to :meth:`~smtpd.SMTPServer.process_message` as a byte string. The default is ``True`` for backward compatibility reasons, but will change to ``False`` in Python 3.6. (Contributed by Maciej Szulik in :issue:`19662`.) * It is now possible to provide, directly or via name resolution, IPv6 addresses in the :class:`~smtpd.SMTPServer` constructor, and have it successfully connect. (Contributed by Milan Oberkirch in :issue:`14758`.) * :mod:`~smtpd.SMTPServer` now supports :rfc:`6531` via the *enable_SMTPUTF8* constructor argument and a user-provided :meth:`~smtpd.SMTPServer.process_smtputf8_message` method. smtplib ------- * A new :meth:`~smtplib.SMTP.auth` method provides a convenient way to implement custom authentication mechanisms. (Contributed by Milan Oberkirch in :issue:`15014`.) sndhdr ------ * :func:`~sndhdr.what` and :func:`~sndhdr.whathdr` now return :func:`~collections.namedtuple`. (Contributed by Claudiu Popa in :issue:`18615`.) socket ------ * New :meth:`socket.socket.sendfile` method allows to send a file over a socket by using high-performance :func:`os.sendfile` function on UNIX resulting in uploads being from 2x to 3x faster than when using plain :meth:`socket.socket.send`. (Contributed by Giampaolo Rodola' in :issue:`17552`.) sysconfig --------- * The user scripts directory on Windows is now versioned. (Contributed by Paul Moore in :issue:`23437`.) tarfile ------- * The :func:`tarfile.open` function now supports ``'x'`` (exclusive creation) mode. (Contributed by Berker Peksag in :issue:`21717`.) time ---- * The :func:`time.monotonic` function is now always available. (Contributed by Victor Stinner in :issue:`22043`.) urllib ------ * A new :class:`urllib.request.HTTPBasicPriorAuthHandler` allows HTTP Basic Authentication credentials to be sent unconditionally with the first HTTP request, rather than waiting for a HTTP 401 Unauthorized response from the server. (Contributed by Matej Cepl in :issue:`19494`.) wsgiref ------- * *headers* parameter of :class:`wsgiref.headers.Headers` is now optional. (Contributed by Pablo Torres Navarrete and SilentGhost in :issue:`5800`.) xmlrpc ------ * :class:`xmlrpc.client.ServerProxy` is now a :term:`context manager`. (Contributed by Claudiu Popa in :issue:`20627`.) Optimizations ============= The following performance enhancements have been added: * Construction of ``bytes(int)`` (filled by zero bytes) is faster and use less memory for large objects. ``calloc()`` is used instead of ``malloc()`` to allocate memory for these objects. * Some operations on :class:`~ipaddress.IPv4Network` and :class:`~ipaddress.IPv6Network` have been massively sped up, such as :meth:`~ipaddress.IPv4Network.subnets`, :meth:`~ipaddress.IPv4Network.supernet`, :func:`~ipaddress.summarize_address_range`, :func:`~ipaddress.collapse_addresses`. The speed up can range from 3x to 15x. (:issue:`21486`, :issue:`21487`, :issue:`20826`) * Many operations on :class:`io.BytesIO` are now 50% to 100% faster. (Contributed by Serhiy Storchaka in :issue:`15381`.) * :func:`marshal.dumps` is now faster (65%-85% with versions 3--4, 20-25% with versions 0--2 on typical data, and up to 5x in best cases). (Contributed by Serhiy Storchaka in :issue:`20416` and :issue:`23344`.) Build and C API Changes ======================= Changes to Python's build process and to the C API include: * New ``calloc`` functions: * :c:func:`PyMem_RawCalloc` * :c:func:`PyMem_Calloc` * :c:func:`PyObject_Calloc` * :c:func:`_PyObject_GC_Calloc` Deprecated ========== Unsupported Operating Systems ----------------------------- * None yet. Deprecated Python modules, functions and methods ------------------------------------------------ * The :mod:`formatter` module has now graduated to full deprecation and is still slated for removal in Python 3.6. * :mod:`smtpd` has in the past always decoded the DATA portion of email messages using the ``utf-8`` codec. This can now be controlled by the new *decode_data* keyword to :class:`~smtpd.SMTPServer`. The default value is ``True``, but this default is deprecated. Specify the *decode_data* keyword with an appropriate value to avoid the deprecation warning. Deprecated functions and types of the C API ------------------------------------------- * None yet. Deprecated features ------------------- * None yet. Removed ======= API and Feature Removals ------------------------ The following obsolete and previously deprecated APIs and features have been removed: * The ``__version__`` attribute has been dropped from the email package. The email code hasn't been shipped separately from the stdlib for a long time, and the ``__version__`` string was not updated in the last few releases. * The internal ``Netrc`` class in the :mod:`ftplib` module was deprecated in 3.4, and has now been removed. (Contributed by Matt Chaput in :issue:`6623`.) Porting to Python 3.5 ===================== This section lists previously described changes and other bugfixes that may require changes to your code. Changes in the Python API ------------------------- * Before Python 3.5, a :class:`datetime.time` object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See :issue:`13936` for full details. * :meth:`ssl.SSLSocket.send()` now raises either :exc:`ssl.SSLWantReadError` or :exc:`ssl.SSLWantWriteError` on a non-blocking socket if the operation would block. Previously, it would return 0. See :issue:`20951`. * The ``__name__`` attribute of generator is now set from the function name, instead of being set from the code name. Use ``gen.gi_code.co_name`` to retrieve the code name. Generators also have a new ``__qualname__`` attribute, the qualified name, which is now used for the representation of a generator (``repr(gen)``). See :issue:`21205`. * The deprecated "strict" mode and argument of :class:`~html.parser.HTMLParser`, :meth:`HTMLParser.error`, and the :exc:`HTMLParserError` exception have been removed. (Contributed by Ezio Melotti in :issue:`15114`.) The *convert_charrefs* argument of :class:`~html.parser.HTMLParser` is now ``True`` by default. (Contributed by Berker Peksag in :issue:`21047`.) * Although it is not formally part of the API, it is worth noting for porting purposes (ie: fixing tests) that error messages that were previously of the form "'sometype' does not support the buffer protocol" are now of the form "a bytes-like object is required, not 'sometype'". (Contributed by Ezio Melotti in :issue:`16518`.) * If the current directory is set to a directory that no longer exists then :exc:`FileNotFoundError` will no longer be raised and instead :meth:`~importlib.machinery.FileFinder.find_spec` will return ``None`` **without** caching ``None`` in :data:`sys.path_importer_cache` which is different than the typical case (:issue:`22834`). * HTTP status code and messages from :mod:`http.client` and :mod:`http.server` were refactored into a common :class:`~http.HTTPStatus` enum. The values in :mod:`http.client` and :mod:`http.server` remain available for backwards compatibility. (Contributed by Demian Brecht in :issue:`21793`.) * When an import loader defines :meth:`~importlib.machinery.Loader.exec_module` it is now expected to also define :meth:`~importlib.machinery.Loader.create_module` (raises a :exc:`DeprecationWarning` now, will be an error in Python 3.6). If the loader inherits from :class:`importlib.abc.Loader` then there is nothing to do, else simply define :meth:`~importlib.machinery.Loader.create_module` to return ``None`` (:issue:`23014`). * :func:`re.split` always ignored empty pattern matches, so the ``'x*'`` pattern worked the same as ``'x+'``, and the ``'\b'`` pattern never worked. Now :func:`re.split` raises a warning if the pattern could match an empty string. For compatibility use patterns that never match an empty string (e.g. ``'x+'`` instead of ``'x*'``). Patterns that could only match an empty string (such as ``'\b'``) now raise an error. Changes in the C API -------------------- * The undocumented :c:member:`~PyMemoryViewObject.format` member of the (non-public) :c:type:`PyMemoryViewObject` structure has been removed. All extensions relying on the relevant parts in ``memoryobject.h`` must be rebuilt. * The :c:type:`PyMemAllocator` structure was renamed to :c:type:`PyMemAllocatorEx` and a new ``calloc`` field was added. * Removed non-documented macro :c:macro:`PyObject_REPR` which leaked references. Use format character ``%R`` in :c:func:`PyUnicode_FromFormat`-like functions to format the :func:`repr` of the object.