1168 lines
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ReStructuredText
1168 lines
47 KiB
ReStructuredText
****************************
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What's New In Python 3.9
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****************************
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:Release: |release|
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:Date: |today|
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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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XXX Describe the transmogrify() function added to the socket
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module.
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(Contributed by P.Y. Developer in :issue:`12345`.)
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This saves the maintainer the effort of going through the Mercurial log
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when researching a change.
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This article explains the new features in Python 3.9, compared to 3.8.
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For full details, see the :ref:`changelog <changelog>`.
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.. note::
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Prerelease users should be aware that this document is currently in draft
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form. It will be updated substantially as Python 3.9 moves towards release,
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so it's worth checking back even after reading earlier versions.
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Summary -- Release highlights
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=============================
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.. This section singles out the most important changes in Python 3.9.
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Brevity is key.
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.. PEP-sized items next.
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You should check for DeprecationWarning in your code
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====================================================
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When Python 2.7 was still supported, many functions were kept for backward
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compatibility with Python 2.7. With the end of Python 2.7 support, these
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backward compatibility layers have been removed, or will be removed soon.
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Most of them emitted a :exc:`DeprecationWarning` warning for several years. For
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example, using ``collections.Mapping`` instead of ``collections.abc.Mapping``
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emits a :exc:`DeprecationWarning` since Python 3.3, released in 2012.
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Test your application with the :option:`-W` ``default`` command-line option to see
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:exc:`DeprecationWarning` and :exc:`PendingDeprecationWarning`, or even with
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:option:`-W` ``error`` to treat them as errors. :ref:`Warnings Filter
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<warning-filter>` can be used to ignore warnings from third-party code.
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It has been decided to keep a few backward compatibility layers for one last
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release, to give more time to Python projects maintainers to organize the
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removal of the Python 2 support and add support for Python 3.9.
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Aliases to :ref:`Abstract Base Classes <collections-abstract-base-classes>` in
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the :mod:`collections` module, like ``collections.Mapping`` alias to
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:class:`collections.abc.Mapping`, are kept for one last release for backward
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compatibility. They will be removed from Python 3.10.
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More generally, try to run your tests in the :ref:`Python Development Mode
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<devmode>` which helps to prepare your code to make it compatible with the
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next Python version.
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New Features
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============
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Dictionary Merge & Update Operators
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-----------------------------------
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Merge (``|``) and update (``|=``) operators have been added to the built-in
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:class:`dict` class. See :pep:`584` for a full description.
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(Contributed by Brandt Bucher in :issue:`36144`.)
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PEP 616: New removeprefix() and removesuffix() string methods
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-------------------------------------------------------------
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:meth:`str.removeprefix(prefix)<str.removeprefix>` and
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:meth:`str.removesuffix(suffix)<str.removesuffix>` have been added
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to easily remove an unneeded prefix or a suffix from a string. Corresponding
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``bytes``, ``bytearray``, and ``collections.UserString`` methods have also been
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added. See :pep:`616` for a full description. (Contributed by Dennis Sweeney in
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:issue:`39939`.)
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PEP 585: Builtin Generic Types
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------------------------------
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In type annotations you can now use built-in collection types such as
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``list`` and ``dict`` as generic types instead of importing the
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corresponding capitalized types (e.g. ``List`` or ``Dict``) from
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``typing``. Some other types in the standard library are also now generic,
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for example ``queue.Queue``.
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Example:
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.. code-block:: python
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def greet_all(names: list[str]) -> None:
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for name in names:
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print("Hello", name)
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See :pep:`585` for more details. (Contributed by Guido van Rossum,
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Ethan Smith, and Batuhan Taşkaya in :issue:`39481`.)
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PEP 617: New Parser
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-------------------
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Python 3.9 uses a new parser, based on `PEG
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<https://en.wikipedia.org/wiki/Parsing_expression_grammar>`_ instead
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of `LL(1) <https://en.wikipedia.org/wiki/LL_parser>`_. The new
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parser's performance is roughly comparable to that of the old parser,
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but the PEG formalism is more flexible than LL(1) when it comes to
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designing new language features. We'll start using this flexibility
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in Python 3.10 and later.
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The :mod:`ast` module uses the new parser and produces the same AST as
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the old parser.
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In Python 3.10, the old parser will be deleted and so will all
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functionality that depends on it (primarily the :mod:`parser` module,
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which has long been deprecated). In Python 3.9 *only*, you can switch
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back to the LL(1) parser using a command line switch (``-X
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oldparser``) or an environment variable (``PYTHONOLDPARSER=1``).
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See :pep:`617` for more details. (Contributed by Guido van Rossum,
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Pablo Galindo and Lysandros Nikolaou in :issue:`40334`.)
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Other Language Changes
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======================
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* :func:`__import__` now raises :exc:`ImportError` instead of
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:exc:`ValueError`, which used to occur when a relative import went past
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its top-level package.
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(Contributed by Ngalim Siregar in :issue:`37444`.)
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* Python now gets the absolute path of the script filename specified on
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the command line (ex: ``python3 script.py``): the ``__file__`` attribute of
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the :mod:`__main__` module became an absolute path, rather than a relative
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path. These paths now remain valid after the current directory is changed
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by :func:`os.chdir`. As a side effect, the traceback also displays the
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absolute path for :mod:`__main__` module frames in this case.
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(Contributed by Victor Stinner in :issue:`20443`.)
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* In the :ref:`Python Development Mode <devmode>` and in debug build, the
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*encoding* and *errors* arguments are now checked for string encoding and
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decoding operations. Examples: :func:`open`, :meth:`str.encode` and
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:meth:`bytes.decode`.
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By default, for best performance, the *errors* argument is only checked at
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the first encoding/decoding error and the *encoding* argument is sometimes
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ignored for empty strings.
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(Contributed by Victor Stinner in :issue:`37388`.)
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* ``"".replace("", s, n)`` now returns ``s`` instead of an empty string for
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all non-zero ``n``. It is now consistent with ``"".replace("", s)``.
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There are similar changes for :class:`bytes` and :class:`bytearray` objects.
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(Contributed by Serhiy Storchaka in :issue:`28029`.)
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* Any valid expression can now be used as a :term:`decorator`. Previously, the
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grammar was much more restrictive. See :pep:`614` for details.
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(Contributed by Brandt Bucher in :issue:`39702`.)
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* Improved help for the :mod:`typing` module. Docstrings are now shown for
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all special forms and special generic aliases (like ``Union`` and ``List``).
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Using :func:`help` with generic alias like ``List[int]`` will show the help
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for the correspondent concrete type (``list`` in this case).
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(Contributed by Serhiy Storchaka in :issue:`40257`.)
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New Modules
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===========
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zoneinfo
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--------
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The :mod:`zoneinfo` module brings support for the IANA time zone database to
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the standard library. It adds :class:`zoneinfo.ZoneInfo`, a concrete
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:class:`datetime.tzinfo` implementation backed by the system's time zone data.
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Example::
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>>> from zoneinfo import ZoneInfo
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>>> from datetime import datetime, timedelta
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>>> # Daylight saving time
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>>> dt = datetime(2020, 10, 31, 12, tzinfo=ZoneInfo("America/Los_Angeles"))
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>>> print(dt)
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2020-10-31 12:00:00-07:00
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>>> dt.tzname()
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'PDT'
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>>> # Standard time
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>>> dt += timedelta(days=7)
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>>> print(dt)
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2020-11-07 12:00:00-08:00
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>>> print(dt.tzname())
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PST
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As a fall-back source of data for platforms that don't ship the IANA database,
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the |tzdata|_ module was released as a first-party package -- distributed via
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PyPI and maintained by the CPython core team.
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.. |tzdata| replace:: ``tzdata``
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.. _tzdata: https://pypi.org/project/tzdata/
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.. seealso::
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:pep:`615` -- Support for the IANA Time Zone Database in the Standard Library
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PEP written and implemented by Paul Ganssle
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graphlib
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---------
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Add the :mod:`graphlib` that contains the :class:`graphlib.TopologicalSorter` class
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to offer functionality to perform topological sorting of graphs. (Contributed by Pablo
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Galindo, Tim Peters and Larry Hastings in :issue:`17005`.)
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Improved Modules
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================
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ast
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---
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Added the *indent* option to :func:`~ast.dump` which allows it to produce a
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multiline indented output.
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(Contributed by Serhiy Storchaka in :issue:`37995`.)
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Added :func:`ast.unparse` as a function in the :mod:`ast` module that can
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be used to unparse an :class:`ast.AST` object and produce a string with code
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that would produce an equivalent :class:`ast.AST` object when parsed.
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(Contributed by Pablo Galindo and Batuhan Taskaya in :issue:`38870`.)
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Added docstrings to AST nodes that contains the ASDL signature used to
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construct that node. (Contributed by Batuhan Taskaya in :issue:`39638`.)
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asyncio
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-------
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Due to significant security concerns, the *reuse_address* parameter of
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:meth:`asyncio.loop.create_datagram_endpoint` is no longer supported. This is
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because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
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details, see the documentation for ``loop.create_datagram_endpoint()``.
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(Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
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:issue:`37228`.)
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Added a new :term:`coroutine` :meth:`~asyncio.loop.shutdown_default_executor`
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that schedules a shutdown for the default executor that waits on the
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:class:`~concurrent.futures.ThreadPoolExecutor` to finish closing. Also,
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:func:`asyncio.run` has been updated to use the new :term:`coroutine`.
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(Contributed by Kyle Stanley in :issue:`34037`.)
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Added :class:`asyncio.PidfdChildWatcher`, a Linux-specific child watcher
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implementation that polls process file descriptors. (:issue:`38692`)
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Added a new :term:`coroutine` :func:`asyncio.to_thread`. It is mainly used for
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running IO-bound functions in a separate thread to avoid blocking the event
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loop, and essentially works as a high-level version of
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:meth:`~asyncio.loop.run_in_executor` that can directly take keyword arguments.
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(Contributed by Kyle Stanley and Yury Selivanov in :issue:`32309`.)
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compileall
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----------
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Added new possibility to use hardlinks for duplicated ``.pyc`` files: *hardlink_dupes* parameter and --hardlink-dupes command line option.
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(Contributed by Lumír 'Frenzy' Balhar in :issue:`40495`.)
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Added new options for path manipulation in resulting ``.pyc`` files: *stripdir*, *prependdir*, *limit_sl_dest* parameters and -s, -p, -e command line options.
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Added the possibility to specify the option for an optimization level multiple times.
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(Contributed by Lumír 'Frenzy' Balhar in :issue:`38112`.)
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concurrent.futures
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------------------
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Added a new *cancel_futures* parameter to
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:meth:`concurrent.futures.Executor.shutdown` that cancels all pending futures
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which have not started running, instead of waiting for them to complete before
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shutting down the executor.
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(Contributed by Kyle Stanley in :issue:`39349`.)
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Removed daemon threads from :class:`~concurrent.futures.ThreadPoolExecutor`
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and :class:`~concurrent.futures.ProcessPoolExecutor`. This improves
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compatibility with subinterpreters and predictability in their shutdown
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processes. (Contributed by Kyle Stanley in :issue:`39812`.)
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Workers in :class:`~concurrent.futures.ProcessPoolExecutor` are now spawned on
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demand, only when there are no available idle workers to reuse. This optimizes
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startup overhead and reduces the amount of lost CPU time to idle workers.
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(Contributed by Kyle Stanley in :issue:`39207`.)
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curses
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------
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Add :func:`curses.get_escdelay`, :func:`curses.set_escdelay`,
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:func:`curses.get_tabsize`, and :func:`curses.set_tabsize` functions.
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(Contributed by Anthony Sottile in :issue:`38312`.)
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datetime
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--------
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The :meth:`~datetime.date.isocalendar()` of :class:`datetime.date`
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and :meth:`~datetime.datetime.isocalendar()` of :class:`datetime.datetime`
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methods now returns a :func:`~collections.namedtuple` instead of a :class:`tuple`.
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(Contributed by Dong-hee Na in :issue:`24416`.)
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distutils
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---------
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The :command:`upload` command now creates SHA2-256 and Blake2b-256 hash
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digests. It skips MD5 on platforms that block MD5 digest.
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(Contributed by Christian Heimes in :issue:`40698`.)
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fcntl
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-----
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Added constants :data:`~fcntl.F_OFD_GETLK`, :data:`~fcntl.F_OFD_SETLK`
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and :data:`~fcntl.F_OFD_SETLKW`.
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(Contributed by Dong-hee Na in :issue:`38602`.)
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ftplib
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-------
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:class:`~ftplib.FTP` and :class:`~ftplib.FTP_TLS` now raise a :class:`ValueError`
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if the given timeout for their constructor is zero to prevent the creation of
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a non-blocking socket. (Contributed by Dong-hee Na in :issue:`39259`.)
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gc
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--
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When the garbage collector makes a collection in which some objects resurrect
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(they are reachable from outside the isolated cycles after the finalizers have
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been executed), do not block the collection of all objects that are still
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unreachable. (Contributed by Pablo Galindo and Tim Peters in :issue:`38379`.)
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Added a new function :func:`gc.is_finalized` to check if an object has been
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finalized by the garbage collector. (Contributed by Pablo Galindo in
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:issue:`39322`.)
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hashlib
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-------
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Builtin hash modules can now be disabled with
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``./configure --without-builtin-hashlib-hashes`` or selectively enabled with
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e.g. ``./configure --with-builtin-hashlib-hashes=sha3,blake2`` to force use
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of OpenSSL based implementation.
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(Contributed by Christian Heimes in :issue:`40479`)
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http
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----
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HTTP status codes ``103 EARLY_HINTS``, ``418 IM_A_TEAPOT`` and ``425 TOO_EARLY`` are added to
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:class:`http.HTTPStatus`. (Contributed by Dong-hee Na in :issue:`39509` and Ross Rhodes in :issue:`39507`.)
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imaplib
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|
-------
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:class:`~imaplib.IMAP4` and :class:`~imaplib.IMAP4_SSL` now have
|
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an optional *timeout* parameter for their constructors.
|
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Also, the :meth:`~imaplib.IMAP4.open` method now has an optional *timeout* parameter
|
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with this change. The overridden methods of :class:`~imaplib.IMAP4_SSL` and
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:class:`~imaplib.IMAP4_stream` were applied to this change.
|
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(Contributed by Dong-hee Na in :issue:`38615`.)
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:meth:`imaplib.IMAP4.unselect` is added.
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:meth:`imaplib.IMAP4.unselect` frees server's resources associated with the
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selected mailbox and returns the server to the authenticated
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state. This command performs the same actions as :meth:`imaplib.IMAP4.close`, except
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that no messages are permanently removed from the currently
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selected mailbox. (Contributed by Dong-hee Na in :issue:`40375`.)
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importlib
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|
---------
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|
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To improve consistency with import statements, :func:`importlib.util.resolve_name`
|
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now raises :exc:`ImportError` instead of :exc:`ValueError` for invalid relative
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import attempts.
|
|
(Contributed by Ngalim Siregar in :issue:`37444`.)
|
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inspect
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-------
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:attr:`inspect.BoundArguments.arguments` is changed from ``OrderedDict`` to regular
|
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dict. (Contributed by Inada Naoki in :issue:`36350` and :issue:`39775`.)
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ipaddress
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---------
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:mod:`ipaddress` now supports IPv6 Scoped Addresses (IPv6 address with suffix ``%<scope_id>``).
|
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Scoped IPv6 addresses can be parsed using :class:`ipaddress.IPv6Address`.
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If present, scope zone ID is available through the :attr:`~ipaddress.IPv6Address.scope_id` attribute.
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(Contributed by Oleksandr Pavliuk in :issue:`34788`.)
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math
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----
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Expanded the :func:`math.gcd` function to handle multiple arguments.
|
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Formerly, it only supported two arguments.
|
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(Contributed by Serhiy Storchaka in :issue:`39648`.)
|
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Add :func:`math.lcm`: return the least common multiple of specified arguments.
|
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(Contributed by Mark Dickinson, Ananthakrishnan and Serhiy Storchaka in
|
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:issue:`39479` and :issue:`39648`.)
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Add :func:`math.nextafter`: return the next floating-point value after *x*
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towards *y*.
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(Contributed by Victor Stinner in :issue:`39288`.)
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Add :func:`math.ulp`: return the value of the least significant bit
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of a float.
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(Contributed by Victor Stinner in :issue:`39310`.)
|
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|
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multiprocessing
|
|
---------------
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The :class:`multiprocessing.SimpleQueue` class has a new
|
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:meth:`~multiprocessing.SimpleQueue.close` method to explicitly close the
|
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queue.
|
|
(Contributed by Victor Stinner in :issue:`30966`.)
|
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|
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nntplib
|
|
-------
|
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:class:`~nntplib.NNTP` and :class:`~nntplib.NNTP_SSL` now raise a :class:`ValueError`
|
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if the given timeout for their constructor is zero to prevent the creation of
|
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a non-blocking socket. (Contributed by Dong-hee Na in :issue:`39259`.)
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os
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--
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Added :data:`~os.CLD_KILLED` and :data:`~os.CLD_STOPPED` for :attr:`si_code`.
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(Contributed by Dong-hee Na in :issue:`38493`.)
|
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Exposed the Linux-specific :func:`os.pidfd_open` (:issue:`38692`) and
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:data:`os.P_PIDFD` (:issue:`38713`) for process management with file
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descriptors.
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|
|
The :func:`os.unsetenv` function is now also available on Windows.
|
|
(Contributed by Victor Stinner in :issue:`39413`.)
|
|
|
|
The :func:`os.putenv` and :func:`os.unsetenv` functions are now always
|
|
available.
|
|
(Contributed by Victor Stinner in :issue:`39395`.)
|
|
|
|
Add :func:`os.waitstatus_to_exitcode` function:
|
|
convert a wait status to an exit code.
|
|
(Contributed by Victor Stinner in :issue:`40094`.)
|
|
|
|
pathlib
|
|
-------
|
|
|
|
Added :meth:`pathlib.Path.readlink()` which acts similarly to
|
|
:func:`os.readlink`.
|
|
(Contributed by Girts Folkmanis in :issue:`30618`)
|
|
|
|
poplib
|
|
------
|
|
|
|
:class:`~poplib.POP3` and :class:`~poplib.POP3_SSL` now raise a :class:`ValueError`
|
|
if the given timeout for their constructor is zero to prevent the creation of
|
|
a non-blocking socket. (Contributed by Dong-hee Na in :issue:`39259`.)
|
|
|
|
pprint
|
|
------
|
|
|
|
:mod:`pprint` can now pretty-print :class:`types.SimpleNamespace`.
|
|
(Contributed by Carl Bordum Hansen in :issue:`37376`.)
|
|
|
|
pydoc
|
|
-----
|
|
|
|
The documentation string is now shown not only for class, function,
|
|
method etc, but for any object that has its own ``__doc__`` attribute.
|
|
(Contributed by Serhiy Storchaka in :issue:`40257`.)
|
|
|
|
random
|
|
------
|
|
|
|
Add a new :attr:`random.Random.randbytes` method: generate random bytes.
|
|
(Contributed by Victor Stinner in :issue:`40286`.)
|
|
|
|
signal
|
|
------
|
|
|
|
Exposed the Linux-specific :func:`signal.pidfd_send_signal` for sending to
|
|
signals to a process using a file descriptor instead of a pid. (:issue:`38712`)
|
|
|
|
smtplib
|
|
-------
|
|
|
|
:class:`~smtplib.SMTP` and :class:`~smtplib.SMTP_SSL` now raise a :class:`ValueError`
|
|
if the given timeout for their constructor is zero to prevent the creation of
|
|
a non-blocking socket. (Contributed by Dong-hee Na in :issue:`39259`.)
|
|
|
|
:class:`~smtplib.LMTP` constructor now has an optional *timeout* parameter.
|
|
(Contributed by Dong-hee Na in :issue:`39329`.)
|
|
|
|
socket
|
|
------
|
|
|
|
The :mod:`socket` module now exports the :data:`~socket.CAN_RAW_JOIN_FILTERS`
|
|
constant on Linux 4.1 and greater.
|
|
(Contributed by Stefan Tatschner and Zackery Spytz in :issue:`25780`.)
|
|
|
|
The socket module now supports the :data:`~socket.CAN_J1939` protocol on
|
|
platforms that support it. (Contributed by Karl Ding in :issue:`40291`.)
|
|
|
|
time
|
|
----
|
|
|
|
On AIX, :func:`~time.thread_time` is now implemented with ``thread_cputime()``
|
|
which has nanosecond resolution, rather than
|
|
``clock_gettime(CLOCK_THREAD_CPUTIME_ID)`` which has a resolution of 10 ms.
|
|
(Contributed by Batuhan Taskaya in :issue:`40192`)
|
|
|
|
sys
|
|
---
|
|
|
|
Add a new :attr:`sys.platlibdir` attribute: name of the platform-specific
|
|
library directory. It is used to build the path of standard library and the
|
|
paths of installed extension modules. It is equal to ``"lib"`` on most
|
|
platforms. On Fedora and SuSE, it is equal to ``"lib64"`` on 64-bit platforms.
|
|
(Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner in :issue:`1294959`.)
|
|
|
|
Previously, :attr:`sys.stderr` was block-buffered when non-interactive. Now
|
|
``stderr`` defaults to always being line-buffered.
|
|
(Contributed by Jendrik Seipp in :issue:`13601`.)
|
|
|
|
tracemalloc
|
|
-----------
|
|
|
|
Added :func:`tracemalloc.reset_peak` to set the peak size of traced memory
|
|
blocks to the current size, to measure the peak of specific pieces of code.
|
|
(Contributed by Huon Wilson in :issue:`40630`.)
|
|
|
|
typing
|
|
------
|
|
|
|
:pep:`593` introduced an :data:`typing.Annotated` type to decorate existing
|
|
types with context-specific metadata and new ``include_extras`` parameter to
|
|
:func:`typing.get_type_hints` to access the metadata at runtime. (Contributed
|
|
by Till Varoquaux and Konstantin Kashin.)
|
|
|
|
unicodedata
|
|
-----------
|
|
|
|
The Unicode database has been updated to version 13.0.0. (:issue:`39926`).
|
|
|
|
venv
|
|
----
|
|
|
|
The activation scripts provided by :mod:`venv` now all specify their prompt
|
|
customization consistently by always using the value specified by
|
|
``__VENV_PROMPT__``. Previously some scripts unconditionally used
|
|
``__VENV_PROMPT__``, others only if it happened to be set (which was the default
|
|
case), and one used ``__VENV_NAME__`` instead.
|
|
(Contributed by Brett Cannon in :issue:`37663`.)
|
|
|
|
xml
|
|
---
|
|
|
|
White space characters within attributes are now preserved when serializing
|
|
:mod:`xml.etree.ElementTree` to XML file. EOLNs are no longer normalized
|
|
to "\n". This is the result of discussion about how to interpret
|
|
section 2.11 of XML spec.
|
|
(Contributed by Mefistotelis in :issue:`39011`.)
|
|
|
|
|
|
Optimizations
|
|
=============
|
|
|
|
* Optimized the idiom for assignment a temporary variable in comprehensions.
|
|
Now ``for y in [expr]`` in comprehensions is as fast as a simple assignment
|
|
``y = expr``. For example:
|
|
|
|
sums = [s for s in [0] for x in data for s in [s + x]]
|
|
|
|
Unlike the ``:=`` operator this idiom does not leak a variable to the
|
|
outer scope.
|
|
|
|
(Contributed by Serhiy Storchaka in :issue:`32856`.)
|
|
|
|
* Optimize signal handling in multithreaded applications. If a thread different
|
|
than the main thread gets a signal, the bytecode evaluation loop is no longer
|
|
interrupted at each bytecode instruction to check for pending signals which
|
|
cannot be handled. Only the main thread of the main interpreter can handle
|
|
signals.
|
|
|
|
Previously, the bytecode evaluation loop was interrupted at each instruction
|
|
until the main thread handles signals.
|
|
(Contributed by Victor Stinner in :issue:`40010`.)
|
|
|
|
* Optimize the :mod:`subprocess` module on FreeBSD using ``closefrom()``.
|
|
(Contributed by Ed Maste, Conrad Meyer, Kyle Evans, Kubilay Kocak and Victor
|
|
Stinner in :issue:`38061`.)
|
|
|
|
Here's a summary of performance improvements from Python 3.4 through Python 3.9:
|
|
|
|
.. code-block:: none
|
|
|
|
Python version 3.4 3.5 3.6 3.7 3.8 3.9
|
|
-------------- --- --- --- --- --- ---
|
|
|
|
Variable and attribute read access:
|
|
read_local 7.1 7.1 5.4 5.1 3.9 4.0
|
|
read_nonlocal 7.1 8.1 5.8 5.4 4.4 4.8
|
|
read_global 15.5 19.0 14.3 13.6 7.6 7.7
|
|
read_builtin 21.1 21.6 18.5 19.0 7.5 7.7
|
|
read_classvar_from_class 25.6 26.5 20.7 19.5 18.4 18.6
|
|
read_classvar_from_instance 22.8 23.5 18.8 17.1 16.4 20.1
|
|
read_instancevar 32.4 33.1 28.0 26.3 25.4 27.7
|
|
read_instancevar_slots 27.8 31.3 20.8 20.8 20.2 24.5
|
|
read_namedtuple 73.8 57.5 45.0 46.8 18.4 23.2
|
|
read_boundmethod 37.6 37.9 29.6 26.9 27.7 45.9
|
|
|
|
Variable and attribute write access:
|
|
write_local 8.7 9.3 5.5 5.3 4.3 4.2
|
|
write_nonlocal 10.5 11.1 5.6 5.5 4.7 4.9
|
|
write_global 19.7 21.2 18.0 18.0 15.8 17.2
|
|
write_classvar 92.9 96.0 104.6 102.1 39.2 43.2
|
|
write_instancevar 44.6 45.8 40.0 38.9 35.5 40.7
|
|
write_instancevar_slots 35.6 36.1 27.3 26.6 25.7 27.7
|
|
|
|
Data structure read access:
|
|
read_list 24.2 24.5 20.8 20.8 19.0 21.1
|
|
read_deque 24.7 25.5 20.2 20.6 19.8 21.6
|
|
read_dict 24.3 25.7 22.3 23.0 21.0 22.5
|
|
read_strdict 22.6 24.3 19.5 21.2 18.9 21.6
|
|
|
|
Data structure write access:
|
|
write_list 27.1 28.5 22.5 21.6 20.0 21.6
|
|
write_deque 28.7 30.1 22.7 21.8 23.5 23.2
|
|
write_dict 31.4 33.3 29.3 29.2 24.7 27.8
|
|
write_strdict 28.4 29.9 27.5 25.2 23.1 29.8
|
|
|
|
Stack (or queue) operations:
|
|
list_append_pop 93.4 112.7 75.4 74.2 50.8 53.9
|
|
deque_append_pop 43.5 57.0 49.4 49.2 42.5 45.5
|
|
deque_append_popleft 43.7 57.3 49.7 49.7 42.8 45.5
|
|
|
|
Timing loop:
|
|
loop_overhead 0.5 0.6 0.4 0.3 0.3 0.3
|
|
|
|
These results were generated from the variable access benchmark script at:
|
|
``Tools/scripts/var_access_benchmark.py``. The benchmark script displays timings
|
|
in nanoseconds. The benchmarks were measured on an
|
|
`Intel® Core™ i7-4960HQ processor
|
|
<https://ark.intel.com/content/www/us/en/ark/products/76088/intel-core-i7-4960hq-processor-6m-cache-up-to-3-80-ghz.html>`_
|
|
running the macOS 64-bit builds found at
|
|
`python.org <https://www.python.org/downloads/mac-osx/>`_.
|
|
|
|
|
|
Deprecated
|
|
==========
|
|
|
|
* The distutils ``bdist_msi`` command is now deprecated, use
|
|
``bdist_wheel`` (wheel packages) instead.
|
|
(Contributed by Hugo van Kemenade in :issue:`39586`.)
|
|
|
|
* Currently :func:`math.factorial` accepts :class:`float` instances with
|
|
non-negative integer values (like ``5.0``). It raises a :exc:`ValueError`
|
|
for non-integral and negative floats. It is now deprecated. In future
|
|
Python versions it will raise a :exc:`TypeError` for all floats.
|
|
(Contributed by Serhiy Storchaka in :issue:`37315`.)
|
|
|
|
* The :mod:`parser` and :mod:`symbol` modules are deprecated and will be
|
|
removed in future versions of Python. For the majority of use cases,
|
|
users can leverage the Abstract Syntax Tree (AST) generation and compilation
|
|
stage, using the :mod:`ast` module.
|
|
|
|
* Using :data:`NotImplemented` in a boolean context has been deprecated,
|
|
as it is almost exclusively the result of incorrect rich comparator
|
|
implementations. It will be made a :exc:`TypeError` in a future version
|
|
of Python.
|
|
(Contributed by Josh Rosenberg in :issue:`35712`.)
|
|
|
|
* The :mod:`random` module currently accepts any hashable type as a
|
|
possible seed value. Unfortunately, some of those types are not
|
|
guaranteed to have a deterministic hash value. After Python 3.9,
|
|
the module will restrict its seeds to :const:`None`, :class:`int`,
|
|
:class:`float`, :class:`str`, :class:`bytes`, and :class:`bytearray`.
|
|
|
|
* Opening the :class:`~gzip.GzipFile` file for writing without specifying
|
|
the *mode* argument is deprecated. In future Python versions it will always
|
|
be opened for reading by default. Specify the *mode* argument for opening
|
|
it for writing and silencing a warning.
|
|
(Contributed by Serhiy Storchaka in :issue:`28286`.)
|
|
|
|
* Deprecated the ``split()`` method of :class:`_tkinter.TkappType` in
|
|
favour of the ``splitlist()`` method which has more consistent and
|
|
predicable behavior.
|
|
(Contributed by Serhiy Storchaka in :issue:`38371`.)
|
|
|
|
* The explicit passing of coroutine objects to :func:`asyncio.wait` has been
|
|
deprecated and will be removed in version 3.11.
|
|
(Contributed by Yury Selivanov and Kyle Stanley in :issue:`34790`.)
|
|
|
|
* binhex4 and hexbin4 standards are now deprecated. The :mod:`binhex` module
|
|
and the following :mod:`binascii` functions are now deprecated:
|
|
|
|
* :func:`~binascii.b2a_hqx`, :func:`~binascii.a2b_hqx`
|
|
* :func:`~binascii.rlecode_hqx`, :func:`~binascii.rledecode_hqx`
|
|
|
|
(Contributed by Victor Stinner in :issue:`39353`.)
|
|
|
|
* :mod:`ast` classes ``slice``, ``Index`` and ``ExtSlice`` are considered deprecated
|
|
and will be removed in future Python versions. ``value`` itself should be
|
|
used instead of ``Index(value)``. ``Tuple(slices, Load())`` should be
|
|
used instead of ``ExtSlice(slices)``.
|
|
(Contributed by Serhiy Storchaka in :issue:`32892`.)
|
|
|
|
* :mod:`ast` classes ``Suite``, ``Param``, ``AugLoad`` and ``AugStore``
|
|
are considered deprecated and will be removed in future Python versions.
|
|
They were not generated by the parser and not accepted by the code
|
|
generator in Python 3.
|
|
(Contributed by Batuhan Taskaya in :issue:`39639` and :issue:`39969`
|
|
and Serhiy Storchaka in :issue:`39988`.)
|
|
|
|
* The :c:func:`PyEval_InitThreads` and :c:func:`PyEval_ThreadsInitialized`
|
|
functions are now deprecated and will be removed in Python 3.11. Calling
|
|
:c:func:`PyEval_InitThreads` now does nothing. The :term:`GIL` is initialized
|
|
by :c:func:`Py_Initialize()` since Python 3.7.
|
|
(Contributed by Victor Stinner in :issue:`39877`.)
|
|
|
|
* Passing ``None`` as the first argument to the :func:`shlex.split` function
|
|
has been deprecated. (Contributed by Zackery Spytz in :issue:`33262`.)
|
|
|
|
* The :mod:`lib2to3` module now emits a :exc:`PendingDeprecationWarning`.
|
|
Python 3.9 switched to a PEG parser (see :pep:`617`), and Python 3.10 may
|
|
include new language syntax that is not parsable by lib2to3's LL(1) parser.
|
|
The ``lib2to3`` module may be removed from the standard library in a future
|
|
Python version. Consider third-party alternatives such as `LibCST`_ or
|
|
`parso`_.
|
|
(Contributed by Carl Meyer in :issue:`40360`.)
|
|
|
|
* The *random* parameter of :func:`random.shuffle` has been deprecated.
|
|
(Contributed by Raymond Hettinger in :issue:`40465`)
|
|
|
|
.. _LibCST: https://libcst.readthedocs.io/
|
|
.. _parso: https://parso.readthedocs.io/
|
|
|
|
Removed
|
|
=======
|
|
|
|
* The erroneous version at :data:`unittest.mock.__version__` has been removed.
|
|
|
|
* :class:`nntplib.NNTP`: ``xpath()`` and ``xgtitle()`` methods have been removed.
|
|
These methods are deprecated since Python 3.3. Generally, these extensions
|
|
are not supported or not enabled by NNTP server administrators.
|
|
For ``xgtitle()``, please use :meth:`nntplib.NNTP.descriptions` or
|
|
:meth:`nntplib.NNTP.description` instead.
|
|
(Contributed by Dong-hee Na in :issue:`39366`.)
|
|
|
|
* :class:`array.array`: ``tostring()`` and ``fromstring()`` methods have been
|
|
removed. They were aliases to ``tobytes()`` and ``frombytes()``, deprecated
|
|
since Python 3.2.
|
|
(Contributed by Victor Stinner in :issue:`38916`.)
|
|
|
|
* The undocumented ``sys.callstats()`` function has been removed. Since Python
|
|
3.7, it was deprecated and always returned :const:`None`. It required a special
|
|
build option ``CALL_PROFILE`` which was already removed in Python 3.7.
|
|
(Contributed by Victor Stinner in :issue:`37414`.)
|
|
|
|
* The ``sys.getcheckinterval()`` and ``sys.setcheckinterval()`` functions have
|
|
been removed. They were deprecated since Python 3.2. Use
|
|
:func:`sys.getswitchinterval` and :func:`sys.setswitchinterval` instead.
|
|
(Contributed by Victor Stinner in :issue:`37392`.)
|
|
|
|
* The C function ``PyImport_Cleanup()`` has been removed. It was documented as:
|
|
"Empty the module table. For internal use only."
|
|
(Contributed by Victor Stinner in :issue:`36710`.)
|
|
|
|
* ``_dummy_thread`` and ``dummy_threading`` modules have been removed. These
|
|
modules were deprecated since Python 3.7 which requires threading support.
|
|
(Contributed by Victor Stinner in :issue:`37312`.)
|
|
|
|
* ``aifc.openfp()`` alias to ``aifc.open()``, ``sunau.openfp()`` alias to
|
|
``sunau.open()``, and ``wave.openfp()`` alias to :func:`wave.open()` have been
|
|
removed. They were deprecated since Python 3.7.
|
|
(Contributed by Victor Stinner in :issue:`37320`.)
|
|
|
|
* The :meth:`~threading.Thread.isAlive()` method of :class:`threading.Thread`
|
|
has been removed. It was deprecated since Python 3.8.
|
|
Use :meth:`~threading.Thread.is_alive()` instead.
|
|
(Contributed by Dong-hee Na in :issue:`37804`.)
|
|
|
|
* Methods ``getchildren()`` and ``getiterator()`` of classes
|
|
:class:`~xml.etree.ElementTree.ElementTree` and
|
|
:class:`~xml.etree.ElementTree.Element` in the :mod:`~xml.etree.ElementTree`
|
|
module have been removed. They were deprecated in Python 3.2.
|
|
Use ``iter(x)`` or ``list(x)`` instead of ``x.getchildren()`` and
|
|
``x.iter()`` or ``list(x.iter())`` instead of ``x.getiterator()``.
|
|
(Contributed by Serhiy Storchaka in :issue:`36543`.)
|
|
|
|
* The old :mod:`plistlib` API has been removed, it was deprecated since Python
|
|
3.4. Use the :func:`~plistlib.load`, :func:`~plistlib.loads`, :func:`~plistlib.dump`, and
|
|
:func:`~plistlib.dumps` functions. Additionally, the *use_builtin_types* parameter was
|
|
removed, standard :class:`bytes` objects are always used instead.
|
|
(Contributed by Jon Janzen in :issue:`36409`.)
|
|
|
|
* The C function ``PyGen_NeedsFinalizing`` has been removed. It was not
|
|
documented, tested, or used anywhere within CPython after the implementation
|
|
of :pep:`442`. Patch by Joannah Nanjekye.
|
|
(Contributed by Joannah Nanjekye in :issue:`15088`)
|
|
|
|
* ``base64.encodestring()`` and ``base64.decodestring()``, aliases deprecated
|
|
since Python 3.1, have been removed: use :func:`base64.encodebytes` and
|
|
:func:`base64.decodebytes` instead.
|
|
(Contributed by Victor Stinner in :issue:`39351`.)
|
|
|
|
* ``fractions.gcd()`` function has been removed, it was deprecated since Python
|
|
3.5 (:issue:`22486`): use :func:`math.gcd` instead.
|
|
(Contributed by Victor Stinner in :issue:`39350`.)
|
|
|
|
* The *buffering* parameter of :class:`bz2.BZ2File` has been removed. Since
|
|
Python 3.0, it was ignored and using it emitted a :exc:`DeprecationWarning`.
|
|
Pass an open file object to control how the file is opened.
|
|
(Contributed by Victor Stinner in :issue:`39357`.)
|
|
|
|
* The *encoding* parameter of :func:`json.loads` has been removed.
|
|
As of Python 3.1, it was deprecated and ignored; using it has emitted a
|
|
:exc:`DeprecationWarning` since Python 3.8.
|
|
(Contributed by Inada Naoki in :issue:`39377`)
|
|
|
|
* ``with (await asyncio.lock):`` and ``with (yield from asyncio.lock):`` statements are
|
|
not longer supported, use ``async with lock`` instead. The same is correct for
|
|
``asyncio.Condition`` and ``asyncio.Semaphore``.
|
|
(Contributed by Andrew Svetlov in :issue:`34793`.)
|
|
|
|
* The :func:`sys.getcounts` function, the ``-X showalloccount`` command line
|
|
option and the ``show_alloc_count`` field of the C structure
|
|
:c:type:`PyConfig` have been removed. They required a special Python build by
|
|
defining ``COUNT_ALLOCS`` macro.
|
|
(Contributed by Victor Stinner in :issue:`39489`.)
|
|
|
|
* The ``_field_types`` attribute of the :class:`typing.NamedTuple` class
|
|
has been removed. It was deprecated since Python 3.8. Use
|
|
the ``__annotations__`` attribute instead.
|
|
(Contributed by Serhiy Storchaka in :issue:`40182`.)
|
|
|
|
* The :meth:`symtable.SymbolTable.has_exec` method has been removed. It was
|
|
deprecated since 2006, and only returning ``False`` when it's called.
|
|
(Contributed by Batuhan Taskaya in :issue:`40208`)
|
|
|
|
|
|
Porting to Python 3.9
|
|
=====================
|
|
|
|
This section lists previously described changes and other bugfixes
|
|
that may require changes to your code.
|
|
|
|
|
|
Changes in the Python API
|
|
-------------------------
|
|
|
|
* :func:`__import__` and :func:`importlib.util.resolve_name` now raise
|
|
:exc:`ImportError` where it previously raised :exc:`ValueError`. Callers
|
|
catching the specific exception type and supporting both Python 3.9 and
|
|
earlier versions will need to catch both using ``except (ImportError, ValueError):``.
|
|
|
|
* The :mod:`venv` activation scripts no longer special-case when
|
|
``__VENV_PROMPT__`` is set to ``""``.
|
|
|
|
* The :meth:`select.epoll.unregister` method no longer ignores the
|
|
:data:`~errno.EBADF` error.
|
|
(Contributed by Victor Stinner in :issue:`39239`.)
|
|
|
|
* The *compresslevel* parameter of :class:`bz2.BZ2File` became keyword-only,
|
|
since the *buffering* parameter has been removed.
|
|
(Contributed by Victor Stinner in :issue:`39357`.)
|
|
|
|
* Simplified AST for subscription. Simple indices will be represented by
|
|
their value, extended slices will be represented as tuples.
|
|
``Index(value)`` will return a ``value`` itself, ``ExtSlice(slices)``
|
|
will return ``Tuple(slices, Load())``.
|
|
(Contributed by Serhiy Storchaka in :issue:`34822`.)
|
|
|
|
* The :mod:`importlib` module now ignores the :envvar:`PYTHONCASEOK`
|
|
environment variable when the :option:`-E` or :option:`-I` command line
|
|
options are being used.
|
|
|
|
* The *encoding* parameter has been added to the classes :class:`ftplib.FTP` and
|
|
:class:`ftplib.FTP_TLS` as a keyword-only parameter, and the default encoding
|
|
is changed from Latin-1 to UTF-8 to follow :rfc:`2640`.
|
|
|
|
* :meth:`asyncio.loop.shutdown_default_executor` has been added to
|
|
:class:`~asyncio.AbstractEventLoop`, meaning alternative event loops that
|
|
inherit from it should have this method defined.
|
|
(Contributed by Kyle Stanley in :issue:`34037`.)
|
|
|
|
* The constant values of future flags in the :mod:`__future__` module
|
|
is updated in order to prevent collision with compiler flags. Previously
|
|
``PyCF_ALLOW_TOP_LEVEL_AWAIT`` was clashing with ``CO_FUTURE_DIVISION``.
|
|
(Contributed by Batuhan Taskaya in :issue:`39562`)
|
|
|
|
* ``array('u')`` now uses ``wchar_t`` as C type instead of ``Py_UNICODE``.
|
|
This change doesn't affect to its behavior because ``Py_UNICODE`` is alias
|
|
of ``wchar_t`` since Python 3.3.
|
|
(Contributed by Inada Naoki in :issue:`34538`.)
|
|
|
|
|
|
Changes in the C API
|
|
--------------------
|
|
|
|
* Instances of heap-allocated types (such as those created with
|
|
:c:func:`PyType_FromSpec` and similar APIs) hold a reference to their type
|
|
object since Python 3.8. As indicated in the "Changes in the C API" of Python
|
|
3.8, for the vast majority of cases, there should be no side effect but for
|
|
types that have a custom :c:member:`~PyTypeObject.tp_traverse` function,
|
|
ensure that all custom ``tp_traverse`` functions of heap-allocated types
|
|
visit the object's type.
|
|
|
|
Example:
|
|
|
|
.. code-block:: c
|
|
|
|
int
|
|
foo_traverse(foo_struct *self, visitproc visit, void *arg) {
|
|
// Rest of the traverse function
|
|
#if PY_VERSION_HEX >= 0x03090000
|
|
// This was not needed before Python 3.9 (Python issue 35810 and 40217)
|
|
Py_VISIT(Py_TYPE(self));
|
|
#endif
|
|
}
|
|
|
|
If your traverse function delegates to ``tp_traverse`` of its base class
|
|
(or another type), ensure that ``Py_TYPE(self)`` is visited only once.
|
|
Note that only heap types are expected to visit the type in ``tp_traverse``.
|
|
|
|
For example, if your ``tp_traverse`` function includes:
|
|
|
|
.. code-block:: c
|
|
|
|
base->tp_traverse(self, visit, arg)
|
|
|
|
then add:
|
|
|
|
.. code-block:: c
|
|
|
|
#if PY_VERSION_HEX >= 0x03090000
|
|
// This was not needed before Python 3.9 (Python issue 35810 and 40217)
|
|
if (base->tp_flags & Py_TPFLAGS_HEAPTYPE) {
|
|
// a heap type's tp_traverse already visited Py_TYPE(self)
|
|
} else {
|
|
Py_VISIT(Py_TYPE(self));
|
|
}
|
|
#else
|
|
|
|
(See :issue:`35810` and :issue:`40217` for more information.)
|
|
|
|
CPython bytecode changes
|
|
------------------------
|
|
|
|
* The :opcode:`LOAD_ASSERTION_ERROR` opcode was added for handling the
|
|
:keyword:`assert` statement. Previously, the assert statement would not work
|
|
correctly if the :exc:`AssertionError` exception was being shadowed.
|
|
(Contributed by Zackery Spytz in :issue:`34880`.)
|
|
|
|
|
|
Build Changes
|
|
=============
|
|
|
|
* Add ``--with-platlibdir`` option to the ``configure`` script: name of the
|
|
platform-specific library directory, stored in the new :attr:`sys.platlibdir`
|
|
attribute. See :attr:`sys.platlibdir` attribute for more information.
|
|
(Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis
|
|
and Victor Stinner in :issue:`1294959`.)
|
|
|
|
* The ``COUNT_ALLOCS`` special build macro has been removed.
|
|
(Contributed by Victor Stinner in :issue:`39489`.)
|
|
|
|
* On non-Windows platforms, the :c:func:`setenv` and :c:func:`unsetenv`
|
|
functions are now required to build Python.
|
|
(Contributed by Victor Stinner in :issue:`39395`.)
|
|
|
|
|
|
C API Changes
|
|
=============
|
|
|
|
New Features
|
|
------------
|
|
|
|
* Add :c:func:`PyFrame_GetCode` function: get a frame code.
|
|
Add :c:func:`PyFrame_GetBack` function: get the frame next outer frame.
|
|
(Contributed by Victor Stinner in :issue:`40421`.)
|
|
|
|
* Add :c:func:`PyFrame_GetLineNumber` to the limited C API.
|
|
(Contributed by Victor Stinner in :issue:`40421`.)
|
|
|
|
* Add :c:func:`PyThreadState_GetInterpreter` and
|
|
:c:func:`PyInterpreterState_Get` functions to get the interpreter.
|
|
Add :c:func:`PyThreadState_GetFrame` function to get the current frame of a
|
|
Python thread state.
|
|
Add :c:func:`PyThreadState_GetID` function: get the unique identifier of a
|
|
Python thread state.
|
|
(Contributed by Victor Stinner in :issue:`39947`.)
|
|
|
|
* Add a new public :c:func:`PyObject_CallNoArgs` function to the C API, which
|
|
calls a callable Python object without any arguments. It is the most efficient
|
|
way to call a callable Python object without any argument.
|
|
(Contributed by Victor Stinner in :issue:`37194`.)
|
|
|
|
* Changes in the limited C API (if ``Py_LIMITED_API`` macro is defined):
|
|
|
|
* Provide :c:func:`Py_EnterRecursiveCall` and :c:func:`Py_LeaveRecursiveCall`
|
|
as regular functions for the limited API. Previously, there were defined as
|
|
macros, but these macros didn't compile with the limited C API which cannot
|
|
access ``PyThreadState.recursion_depth`` field (the structure is opaque in
|
|
the limited C API).
|
|
|
|
* ``PyObject_INIT()`` and ``PyObject_INIT_VAR()`` become regular "opaque"
|
|
function to hide implementation details.
|
|
|
|
(Contributed by Victor Stinner in :issue:`38644` and :issue:`39542`.)
|
|
|
|
* The :c:func:`PyModule_AddType` function is added to help adding a type
|
|
to a module.
|
|
(Contributed by Dong-hee Na in :issue:`40024`.)
|
|
|
|
* Add the functions :c:func:`PyObject_GC_IsTracked` and
|
|
:c:func:`PyObject_GC_IsFinalized` to the public API to allow to query if
|
|
Python objects are being currently tracked or have been already finalized by
|
|
the garbage collector respectively. (Contributed by Pablo Galindo in
|
|
:issue:`40241`.)
|
|
|
|
|
|
Porting to Python 3.9
|
|
---------------------
|
|
|
|
* ``PyInterpreterState.eval_frame`` (:pep:`523`) now requires a new mandatory
|
|
*tstate* parameter (``PyThreadState*``).
|
|
(Contributed by Victor Stinner in :issue:`38500`.)
|
|
|
|
* Extension modules: :c:member:`~PyModuleDef.m_traverse`,
|
|
:c:member:`~PyModuleDef.m_clear` and :c:member:`~PyModuleDef.m_free`
|
|
functions of :c:type:`PyModuleDef` are no longer called if the module state
|
|
was requested but is not allocated yet. This is the case immediately after
|
|
the module is created and before the module is executed
|
|
(:c:data:`Py_mod_exec` function). More precisely, these functions are not called
|
|
if :c:member:`~PyModuleDef.m_size` is greater than 0 and the module state (as
|
|
returned by :c:func:`PyModule_GetState`) is ``NULL``.
|
|
|
|
Extension modules without module state (``m_size <= 0``) are not affected.
|
|
|
|
* If :c:func:`Py_AddPendingCall` is called in a subinterpreter, the function is
|
|
now scheduled to be called from the subinterpreter, rather than being called
|
|
from the main interpreter. Each subinterpreter now has its own list of
|
|
scheduled calls.
|
|
(Contributed by Victor Stinner in :issue:`39984`.)
|
|
|
|
* The Windows registry is no longer used to initialize :data:`sys.path` when
|
|
the ``-E`` option is used (if :c:member:`PyConfig.use_environment` is set to
|
|
``0``). This is significant when embedding Python on Windows.
|
|
(Contributed by Zackery Spytz in :issue:`8901`.)
|
|
|
|
* The global variable :c:data:`PyStructSequence_UnnamedField` is now a constant
|
|
and refers to a constant string.
|
|
(Contributed by Serhiy Storchaka in :issue:`38650`.)
|
|
|
|
* The :c:type:`PyGC_Head` structure is now opaque. It is only defined in the
|
|
internal C API (``pycore_gc.h``).
|
|
(Contributed by Victor Stinner in :issue:`40241`.)
|
|
|
|
|
|
Removed
|
|
-------
|
|
|
|
* Exclude ``PyFPE_START_PROTECT()`` and ``PyFPE_END_PROTECT()`` macros of
|
|
``pyfpe.h`` from the limited C API.
|
|
(Contributed by Victor Stinner in :issue:`38835`.)
|
|
|
|
* The ``tp_print`` slot of :ref:`PyTypeObject <type-structs>` has been removed.
|
|
It was used for printing objects to files in Python 2.7 and before. Since
|
|
Python 3.0, it has been ignored and unused.
|
|
(Contributed by Jeroen Demeyer in :issue:`36974`.)
|
|
|
|
* Changes in the limited C API (if ``Py_LIMITED_API`` macro is defined):
|
|
|
|
* Exclude the following functions from the limited C API:
|
|
|
|
* ``PyThreadState_DeleteCurrent()``
|
|
(Contributed by Joannah Nanjekye in :issue:`37878`.)
|
|
* ``_Py_CheckRecursionLimit``
|
|
* ``_Py_NewReference()``
|
|
* ``_Py_ForgetReference()``
|
|
* ``_PyTraceMalloc_NewReference()``
|
|
* ``_Py_GetRefTotal()``
|
|
* The trashcan mechanism which never worked in the limited C API.
|
|
* ``PyTrash_UNWIND_LEVEL``
|
|
* ``Py_TRASHCAN_BEGIN_CONDITION``
|
|
* ``Py_TRASHCAN_BEGIN``
|
|
* ``Py_TRASHCAN_END``
|
|
* ``Py_TRASHCAN_SAFE_BEGIN``
|
|
* ``Py_TRASHCAN_SAFE_END``
|
|
|
|
* Move following functions and definitions to the internal C API:
|
|
|
|
* ``_PyDebug_PrintTotalRefs()``
|
|
* ``_Py_PrintReferences()``
|
|
* ``_Py_PrintReferenceAddresses()``
|
|
* ``_Py_tracemalloc_config``
|
|
* ``_Py_AddToAllObjects()`` (specific to ``Py_TRACE_REFS`` build)
|
|
|
|
(Contributed by Victor Stinner in :issue:`38644` and :issue:`39542`.)
|
|
|
|
* Remove ``_PyRuntime.getframe`` hook and remove ``_PyThreadState_GetFrame``
|
|
macro which was an alias to ``_PyRuntime.getframe``. They were only exposed
|
|
by the internal C API. Remove also ``PyThreadFrameGetter`` type.
|
|
(Contributed by Victor Stinner in :issue:`39946`.)
|
|
|
|
* Remove the following functions from the C API. Call :c:func:`PyGC_Collect`
|
|
explicitly to clear all free lists.
|
|
(Contributed by Inada Naoki and Victor Stinner in :issue:`37340`,
|
|
:issue:`38896` and :issue:`40428`.)
|
|
|
|
* ``PyAsyncGen_ClearFreeLists()``
|
|
* ``PyContext_ClearFreeList()``
|
|
* ``PyDict_ClearFreeList()``
|
|
* ``PyFloat_ClearFreeList()``
|
|
* ``PyFrame_ClearFreeList()``
|
|
* ``PyList_ClearFreeList()``
|
|
* ``PyMethod_ClearFreeList()`` and ``PyCFunction_ClearFreeList()``:
|
|
the free lists of bound method objects have been removed.
|
|
* ``PySet_ClearFreeList()``: the set free list has been removed
|
|
in Python 3.4.
|
|
* ``PyTuple_ClearFreeList()``
|
|
* ``PyUnicode_ClearFreeList()``: the Unicode free list has been removed in
|
|
Python 3.3.
|
|
|
|
* Remove ``_PyUnicode_ClearStaticStrings()`` function.
|
|
(Contributed by Victor Stinner in :issue:`39465`.)
|