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Python 3.12.0 rc3 (final release candidate I promise!) now available

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Thomas Wouters

Sep 19, 2023, 7:30:58 AM9/19/23
I'm pleased to announce the release of Python 3.12 release candidate 3.

This is the second release candidate of Python 3.12.0

This release, *3.12.0rc3*, is the absolutely last release preview for
Python 3.12.

There will be *no ABI changes* from this point forward in the 3.12 series.
The intent is for the final release of 3.12.0, scheduled for Monday,
2023-10-02, to be identical to this release candidate. *This really is the
last chance to find critical problems in Python 3.12.*
to action

We strongly encourage maintainers of third-party Python projects to prepare
their projects for 3.12 compatibilities during this phase, and where
necessary publish Python 3.12 wheels on PyPI to be ready for the final
release of 3.12.0. Any binary wheels built against Python 3.12.0rc3 will
work with future versions of Python 3.12. As always, report any issues to the
Python bug tracker <>.

Please keep in mind that this is a preview release and while it’s as close
to the final release as we can get it, its use is *not* recommended for
production environments.
developers: time to work on documentation now

- Are all your changes properly documented?
- Are they mentioned in What’s New
- Did you notice other changes you know of to have insufficient

new features of the 3.12 series, compared to 3.11

- More flexible f-string parsing
allowing many things previously disallowed (PEP 701
- Support for the buffer protocol
in Python code (PEP 688 <>).
- A new debugging/profiling API
(PEP 669 <>).
- Support for isolated subinterpreters
with separate Global Interpreter Locks (PEP 684
- Even more improved error messages
More exceptions potentially caused by typos now make suggestions to the
- Support for the Linux perf profiler
<> to report
Python function names in traces.
- Many large and small performance improvements
<> (like PEP
709 <> and support for the BOLT binary
optimizer), delivering an estimated 5% overall performance


- New type annotation syntax
for generic classes (PEP 695 <>).
- New override decorator
for methods (PEP 698 <>).


- The deprecated wstr and wstr_length members of the C implementation of
unicode objects were removed, per PEP 623
- In the unittest module, a number of long deprecated methods and
classes were removed. (They had been deprecated since Python 3.1 or 3.2).
- The deprecated smtpd and distutils modules have been removed (see PEP
594 <> and PEP 632
<>. The setuptools package continues to
provide the distutils module.
- A number of other old, broken and deprecated functions, classes and
methods <> have
been removed.
- Invalid backslash escape sequences in strings now warn with
SyntaxWarning instead of DeprecationWarning, making them more visible.
(They will become syntax errors in the future.)
- The internal representation of integers has changed in preparation for
performance enhancements. (This should not affect most users as it is an
internal detail, but it may cause problems for Cython-generated code.)

(Hey, *fellow core developer,* if a feature you find important is missing
from this list, let Thomas know <>.)

For more details on the changes to Python 3.12, see What’s new in Python
3.12 <>. The next scheduled
release of Python 3.12 will be 3.12.0, the *final release*, currently
scheduled for 2023-10-02.

- Online Documentation <>.
- PEP 693 <>, the Python 3.12
Release Schedule.
- Report bugs via GitHub Issues
- Help fund Python and its community

hope you enjoy the new releases!

Thanks to all of the many volunteers who help make Python Development and
these releases possible! Please consider supporting our efforts by
volunteering yourself or through organization contributions to the Python
Software Foundation <>.

Your release team,
Thomas Wouters
Ned Deily
Steve Dower
Łukasz Langa

Thomas Wouters <>
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