731 lines
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ReStructuredText
731 lines
29 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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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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New Modules
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===========
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* None yet.
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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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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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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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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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functools
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---------
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Add the :class:`functools.TopologicalSorter` class to offer functionality to perform
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topological sorting of graphs. (Contributed by Pablo Galindo, Tim Peters and Larry
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Hastings in :issue:`17005`.)
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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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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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importlib
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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.
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(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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nntplib
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-------
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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.
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(Contributed by Victor Stinner in :issue:`39413`.)
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The :func:`os.putenv` and :func:`os.unsetenv` functions are now always
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available.
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(Contributed by Victor Stinner in :issue:`39395`.)
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pathlib
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-------
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Added :meth:`pathlib.Path.readlink()` which acts similarly to
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:func:`os.readlink`.
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(Contributed by Girts Folkmanis in :issue:`30618`)
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poplib
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------
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:class:`~poplib.POP3` and :class:`~poplib.POP3_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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pprint
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------
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:mod:`pprint` can now pretty-print :class:`types.SimpleNamespace`.
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(Contributed by Carl Bordum Hansen in :issue:`37376`.)
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signal
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------
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Exposed the Linux-specific :func:`signal.pidfd_send_signal` for sending to
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signals to a process using a file descriptor instead of a pid. (:issue:`38712`)
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smtplib
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-------
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:class:`~smtplib.SMTP` and :class:`~smtplib.SMTP_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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:class:`~smtplib.LMTP` constructor now has an optional *timeout* parameter.
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(Contributed by Dong-hee Na in :issue:`39329`.)
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threading
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---------
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In a subinterpreter, spawning a daemon thread now raises a :exc:`RuntimeError`. Daemon
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threads were never supported in subinterpreters. Previously, the subinterpreter
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finalization crashed with a Python fatal error if a daemon thread was still
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running.
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(Contributed by Victor Stinner in :issue:`37266`.)
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sys
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---
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Add a new :attr:`sys.platlibdir` attribute: name of the platform-specific
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library directory. It is used to build the path of platform-specific dynamic
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libraries and the path of the standard library. It is equal to ``"lib"`` on
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most platforms. On Fedora and SuSE, it is equal to ``"lib64"`` on 64-bit
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platforms.
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(Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner in :issue:`1294959`.)
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typing
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------
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:pep:`593` introduced an :data:`typing.Annotated` type to decorate existing
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types with context-specific metadata and new ``include_extras`` parameter to
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:func:`typing.get_type_hints` to access the metadata at runtime. (Contributed
|
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by Till Varoquaux and Konstantin Kashin.)
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unicodedata
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-----------
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The Unicode database has been updated to version 13.0.0. (:issue:`39926`).
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venv
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----
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The activation scripts provided by :mod:`venv` now all specify their prompt
|
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customization consistently by always using the value specified by
|
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``__VENV_PROMPT__``. Previously some scripts unconditionally used
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``__VENV_PROMPT__``, others only if it happened to be set (which was the default
|
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case), and one used ``__VENV_NAME__`` instead.
|
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(Contributed by Brett Cannon in :issue:`37663`.)
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Optimizations
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=============
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* Optimized the idiom for assignment a temporary variable in comprehensions.
|
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Now ``for y in [expr]`` in comprehensions is as fast as a simple assignment
|
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``y = expr``. For example:
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sums = [s for s in [0] for x in data for s in [s + x]]
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Unlike to the ``:=`` operator this idiom does not leak a variable to the
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outer scope.
|
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(Contributed by Serhiy Storchaka in :issue:`32856`.)
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Build and C API Changes
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=======================
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* New :c:func:`PyThreadState_GetInterpreter` and
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:c:func:`PyInterpreterState_Get` functions to get the interpreter.
|
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* Add ``--with-platlibdir`` option to the ``configure`` script: name of the
|
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platform-specific library directory, stored in the new :attr:`sys.platlibdir`
|
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attribute. See :attr:`sys.platlibdir` attribute for more information.
|
|
(Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner in :issue:`1294959`.)
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* Add a new public :c:func:`PyObject_CallNoArgs` function to the C API, which
|
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calls a callable Python object without any arguments. It is the most efficient
|
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way to call a callable Python object without any argument.
|
|
(Contributed by Victor Stinner in :issue:`37194`.)
|
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* The global variable :c:data:`PyStructSequence_UnnamedField` is now a constant
|
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and refers to a constant string.
|
|
(Contributed by Serhiy Storchaka in :issue:`38650`.)
|
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* Exclude ``PyFPE_START_PROTECT()`` and ``PyFPE_END_PROTECT()`` macros of
|
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``pyfpe.h`` from ``Py_LIMITED_API`` (stable API).
|
|
(Contributed by Victor Stinner in :issue:`38835`.)
|
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* Remove ``PyMethod_ClearFreeList()`` and ``PyCFunction_ClearFreeList()``
|
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functions: the free lists of bound method objects have been removed.
|
|
(Contributed by Inada Naoki and Victor Stinner in :issue:`37340`.)
|
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* Remove ``PyUnicode_ClearFreeList()`` function: the Unicode free list has been
|
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removed in Python 3.3.
|
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(Contributed by Victor Stinner in :issue:`38896`.)
|
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* The ``tp_print`` slot of :ref:`PyTypeObject <type-structs>` has been removed.
|
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It was used for printing objects to files in Python 2.7 and before. Since
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Python 3.0, it has been ignored and unused.
|
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(Contributed by Jeroen Demeyer in :issue:`36974`.)
|
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* On non-Windows platforms, the :c:func:`setenv` and :c:func:`unsetenv`
|
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functions are now required to build Python.
|
|
(Contributed by Victor Stinner in :issue:`39395`.)
|
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* The ``COUNT_ALLOCS`` special build macro has been removed.
|
|
(Contributed by Victor Stinner in :issue:`39489`.)
|
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* Changes in the limited C API (if ``Py_LIMITED_API`` macro is defined):
|
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* Provide :c:func:`Py_EnterRecursiveCall` and :c:func:`Py_LeaveRecursiveCall`
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as regular functions for the limited API. Previously, there were defined as
|
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macros, but these macros didn't compile with the limited C API which cannot
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access ``PyThreadState.recursion_depth`` field (the structure is opaque in
|
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the limited C API).
|
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* Exclude the following functions from the limited C API:
|
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|
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* ``_Py_CheckRecursionLimit``
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* ``_Py_NewReference()``
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* ``_Py_ForgetReference()``
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* ``_PyTraceMalloc_NewReference()``
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* ``_Py_GetRefTotal()``
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* The trashcan mechanism which never worked in the limited C API.
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* ``PyTrash_UNWIND_LEVEL``
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* ``Py_TRASHCAN_BEGIN_CONDITION``
|
|
* ``Py_TRASHCAN_BEGIN``
|
|
* ``Py_TRASHCAN_END``
|
|
* ``Py_TRASHCAN_SAFE_BEGIN``
|
|
* ``Py_TRASHCAN_SAFE_END``
|
|
|
|
* The following static inline functions or macros become regular "opaque"
|
|
function to hide implementation details:
|
|
|
|
* ``_Py_NewReference()``
|
|
* ``PyObject_INIT()`` and ``PyObject_INIT_VAR()`` become aliases to
|
|
:c:func:`PyObject_Init` and :c:func:`PyObject_InitVar` in the limited C
|
|
API, but are overriden with static inline function otherwise. Thanks to
|
|
that, it was possible to exclude ``_Py_NewReference()`` from the limited
|
|
C API.
|
|
|
|
* 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`.)
|
|
|
|
* ``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.
|
|
|
|
|
|
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` module is 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 :`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 ``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`.)
|
|
|
|
* 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`.)
|
|
|
|
|
|
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()``.
|
|
The ``xml.etree.cElementTree`` module has been removed.
|
|
(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 ``PyThreadState_DeleteCurrent()`` has been removed. It was not documented.
|
|
(Contributed by Joannah Nanjekye in :issue:`37878`.)
|
|
|
|
* 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 ``ast.Suite``, ``ast.Param``, ``ast.AugLoad`` and ``ast.AugStore``
|
|
node classes have been removed due to no longer being needed.
|
|
(Contributed by Batuhan Taskaya in :issue:`39639` and :issue:`39969`
|
|
and Serhiy Storchaka in :issue:`39988`.)
|
|
|
|
|
|
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.
|
|
|
|
|
|
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`.)
|