142 lines
3.9 KiB
ReStructuredText
142 lines
3.9 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 :source:`Misc/NEWS` file.
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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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New Features
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============
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Other Language Changes
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======================
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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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threading
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---------
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In a subinterpreter, spawning a daemon thread now raises an exception. Daemon
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threads were never supported in subinterpreters. Previously, the subinterpreter
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finalization crashed with a Pyton fatal error if a daemon thread was still
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running.
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Optimizations
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=============
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Build and C API Changes
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=======================
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* Add a new public :c:func:`PyObject_CallNoArgs` function to the C API:
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call 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.
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(Contributed by Victor Stinner in :issue:`37194`.)
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Deprecated
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==========
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* Currently :func:`math.factorial` accepts :class:`float` instances with
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non-negative integer values (like ``5.0``). It raises a :exc:`ValueError`
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for non-integral and negative floats. It is deprecated now. In future
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Python versions it will raise a :exc:`TypeError` for all floats.
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(Contributed by Serhiy Storchaka in :issue:`37315`.)
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Removed
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=======
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* ``_dummy_thread`` and ``dummy_threading`` modules have been removed. These
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modules were deprecated since Python 3.7 which requires threading support.
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(Contributed by Victor Stinner in :issue:`37312`.)
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* ``aifc.openfp()`` alias to ``aifc.open()``, ``sunau.openfp()`` alias to
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``sunau.open()``, and ``wave.openfp()`` alias to ``wave.open()`` have been
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removed. They were deprecated since Python 3.7.
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(Contributed by Victor Stinner in :issue:`37320`.)
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Porting to Python 3.9
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=====================
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This section lists previously described changes and other bugfixes
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that may require changes to your code.
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