cpython/Doc/whatsnew/3.6.rst

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****************************
What's New In Python 3.6
****************************
: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 3.6, compared to 3.5.
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 3.6 moves towards release,
so it's worth checking back even after reading earlier versions.
Summary -- Release highlights
=============================
.. This section singles out the most important changes in Python 3.6.
Brevity is key.
* None yet.
.. 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
Other Language Changes
======================
* None yet.
New Modules
===========
* None yet.
Improved Modules
================
datetime
--------
The :meth:`datetime.strftime() <datetime.datetime.strftime>` and
:meth:`date.strftime() <datetime.date.strftime>` methods now support ISO 8601 date
directives ``%G``, ``%u`` and ``%V``.
(Contributed by Ashley Anderson in :issue:`12006`.)
pickle
------
Objects that need calling ``__new__`` with keyword arguments can now be pickled
using :ref:`pickle protocols <pickle-protocols>` older than protocol version 4.
Protocol version 4 already supports this case. (Contributed by Serhiy
Storchaka in :issue:`24164`.)
rlcompleter
-----------
Private and special attribute names now are omitted unless the prefix starts
with underscores. A space or a colon is added after some completed keywords.
(Contributed by Serhiy Storchaka in :issue:`25011` and :issue:`25209`.)
Names of most attributes listed by :func:`dir` are now completed.
Previously, names of properties and slots which were not yet created on
an instance were excluded. (Contributed by Martin Panter in :issue:`25590`.)
telnetlib
---------
:class:`~telnetlib.Telnet` is now a context manager (contributed by
Stéphane Wirtel in :issue:`25485`).
urllib.robotparser
------------------
:class:`~urllib.robotparser.RobotFileParser` now supports the ``Crawl-delay`` and
``Request-rate`` extensions.
(Contributed by Nikolay Bogoychev in :issue:`16099`.)
Optimizations
=============
* The ASCII decoder is now up to 60 times as fast for error handlers
``surrogateescape``, ``ignore`` and ``replace`` (Contributed
by Victor Stinner in :issue:`24870`).
* The ASCII and the Latin1 encoders are now up to 3 times as fast for the
error handler ``surrogateescape`` (Contributed by Victor Stinner in :issue:`25227`).
* The UTF-8 encoder is now up to 75 times as fast for error handlers
``ignore``, ``replace``, ``surrogateescape``, ``surrogatepass`` (Contributed
by Victor Stinner in :issue:`25267`).
* The UTF-8 decoder is now up to 15 times as fast for error handlers
``ignore``, ``replace`` and ``surrogateescape`` (Contributed
by Victor Stinner in :issue:`25301`).
* ``bytes % args`` is now up to 2 times faster. (Contributed by Victor Stinner
in :issue:`25349`).
* ``bytearray % args`` is now between 2.5 and 5 times faster. (Contributed by
Victor Stinner in :issue:`25399`).
* Optimize :meth:`bytes.fromhex` and :meth:`bytearray.fromhex`: they are now
between 2x and 3.5x faster. (Contributed by Victor Stinner in :issue:`25401`).
Build and C API Changes
=======================
* New :c:func:`Py_FinalizeEx` API which indicates if flushing buffered data
failed (:issue:`5319`).
Deprecated
==========
New Keywords
------------
``async`` and ``await`` are not recommended to be used as variable, class,
function or module names. Introduced by :pep:`492` in Python 3.5, they will
become proper keywords in Python 3.7.
Deprecated Python modules, functions and methods
------------------------------------------------
* :meth:`importlib.machinery.SourceFileLoader` and
:meth:`importlib.machinery.SourcelessFileLoader` are now deprecated. They
were the only remaining implementations of
:meth:`importlib.abc.Loader.load_module` in :mod:`importlib` that had not
been deprecated in previous versions of Python in favour of
:meth:`importlib.abc.Loader.exec_module`.
Deprecated functions and types of the C API
-------------------------------------------
* None yet.
Deprecated features
-------------------
* The ``pyvenv`` script has been deprecated in favour of ``python3 -m venv``.
This prevents confusion as to what Python interpreter ``pyvenv`` is
connected to and thus what Python interpreter will be used by the virtual
environment. See :issue:`25154`.
Removed
=======
API and Feature Removals
------------------------
* ``inspect.getargspec()`` was removed (was deprecated since CPython 3.0).
:func:`inspect.getfullargspec` is an almost drop in replacement.
* ``inspect.getmoduleinfo()`` was removed (was deprecated since CPython 3.3).
:func:`inspect.getmodulename` should be used for obtaining the module
name for a given path.
Porting to Python 3.6
=====================
This section lists previously described changes and other bugfixes
that may require changes to your code.
Changes in the Python API
-------------------------
* The functions in the :mod:`compileall` module now return booleans instead
of ``1`` or ``0`` to represent success or failure, respectively. Thanks to
booleans being a subclass of integers, this should only be an issue if you
were doing identity checks for ``1`` or ``0``. See :issue:`25768`.
* Reading the :attr:`~urllib.parse.SplitResult.port` attribute of
:func:`urllib.parse.urlsplit` and :func:`~urllib.parse.urlparse` results
now raises :exc:`ValueError` for out-of-range values, rather than
returning :const:`None`. See :issue:`20059`.
* The :mod:`imp` module now raises a :exc:`DeprecationWarning` instead of
:exc:`PendingDeprecationWarning`.
* The following modules have had missing APIs added to their :attr:`__all__`
attributes to match the documented APIs: :mod:`csv`, :mod:`enum`,
:mod:`ftplib`, :mod:`logging`, :mod:`optparse`, :mod:`threading` and
:mod:`wave`. This means they will export new symbols when ``import *``
is used. See :issue:`23883`.
Changes in the C API
--------------------
* :c:func:`Py_Exit` (and the main interpreter) now override the exit status
with 120 if flushing buffered data failed. See :issue:`5319`.