[RELEASE] Python 3.13.0 release candidate 1 released

Python 3.13 *release candidate 1* is now available.

https://www.python.org/downloads/release/python-3130rc1/

<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-this-is-the-first-release-candidate-of-python-3130-1>This
is the first release candidate of Python 3.13.0

This release, *3.13.0rc1*, is the penultimate release preview. Entering the
release candidate phase, only reviewed code changes which are clear bug
fixes are allowed between this release candidate and the final release. The
second candidate (and the last planned release preview) is scheduled for
Tuesday, 2024-09-03, while the official release of 3.13.0 is scheduled for
Tuesday, 2024-10-01.

There will be *no ABI changes* from this point forward in the 3.13 series,
and the goal is that there will be as few code changes as possible.
<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-call-to-action-2>Call
to action

We strongly encourage maintainers of third-party Python projects to prepare
their projects for 3.13 compatibilities during this phase, and where
necessary publish Python 3.13 wheels on PyPI to be ready for the final
release of 3.13.0. Any binary wheels built against Python 3.13.0rc1 *will
work* with future versions of Python 3.13. As always, report any issues to the
Python bug tracker <https://github.com/python/cpython/issues>.

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.
<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-core-developers-time-to-work-on-documentation-now-3>Core
developers: time to work on documentation now

   - Are all your changes properly documented?
   - Are they mentioned in What’s New
   <https://docs.python.org/3.13/whatsnew/3.13.html>?
   - Did you notice other changes you know of to have insufficient
   documentation?

<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-major-new-features-of-the-313-series-compared-to-312-4>Major
new features of the 3.13 series, compared to 3.12

Some of the new major new features and changes in Python 3.13 are:
<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-new-features-5>New
features

   - A new and improved interactive interpreter
   <https://docs.python.org/3.13/whatsnew/3.13.html#a-better-interactive-interpreter>,
   based on PyPy <https://pypy.org>’s, featuring multi-line editing and
   color support, as well as colorized exception tracebacks
   <https://docs.python.org/3.13/whatsnew/3.13.html#improved-error-messages>
   .
   - An *experimental* free-threaded build mode
   <https://docs.python.org/3.13/whatsnew/3.13.html#free-threaded-cpython>,
   which disables the Global Interpreter Lock, allowing threads to run more
   concurrently. The build mode is available as an experimental feature in the
   Windows and macOS installers as well.
   - A preliminary, *experimental* JIT
   <https://docs.python.org/3.13/whatsnew/3.13.html#experimental-jit-compiler>,
   providing the ground work for significant performance improvements.
   - The locals() builtin function (and its C equivalent) now has well-defined
   semantics when mutating the returned mapping
   <https://docs.python.org/3.13/whatsnew/3.13.html#defined-mutation-semantics-for-locals>,
   which allows debuggers to operate more consistently.
   - The (cyclic) garbage collector is now incremental
   <https://docs.python.org/3.13/whatsnew/3.13.html#incremental-garbage-collection>,
   which should mean shorter pauses for collection in programs with a lot of
   objects.
   - A modified version of mimalloc <https://github.com/microsoft/mimalloc>
   is now included, optional but enabled by default if supported by the
   platform, and required for the free-threaded build mode.
   - Docstrings now have their leading indentation stripped
   <https://docs.python.org/3.13/whatsnew/3.13.html#other-language-changes>,
   reducing memory use and the size of .pyc files. (Most tools handling
   docstrings already strip leading indentation.)
   - The dbm module <https://docs.python.org/3.13/library/dbm.html> has a
   new dbm.sqlite3 backend
   <https://docs.python.org/3.13/whatsnew/3.13.html#dbm> that is used by
   default when creating new files.
   - The minimum supported macOS version was changed from 10.9 to *10.13
   (High Sierra)*. Older macOS versions will not be supported going forward..
   - WASI is now a Tier 2 supported platform
   <https://peps.python.org/pep-0011/#tier-2>. Emscripten is no longer
an officially
   supported platform
   <https://peps.python.org/pep-0011/#no-longer-supported-platforms> (but
   Pyodide <https://pyodide.org> continues to support Emscripten).
   - iOS is now a Tier 3 supported platform
   <https://peps.python.org/pep-0730/>, with Android on the way as well
   <https://peps.python.org/pep-0738/>.

<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-typing-6>
Typing

   - Support for type defaults in type parameters
   <https://peps.python.org/pep-0696/>.
   - A new type narrowing annotation <https://peps.python.org/pep-0742/>,
   typing.TypeIs.
   - A new annotation for read-only items in TypeDicts
   <https://peps.python.org/pep-0705/>.
   - A new annotation for marking deprecations in the type system
   <https://peps.python.org/pep-0702>.

<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-removals-and-new-deprecations-7>Removals
and new deprecations

   - PEP 594 (Removing dead batteries from the standard library)
   <https://peps.python.org/pep-0594/> scheduled removals of many
   deprecated modules: aifc, audioop, chunk, cgi, cgitb, crypt, imghdr,
   mailcap, msilib, nis, nntplib, ossaudiodev, pipes, sndhdr, spwd, sunau,
   telnetlib, uu, xdrlib, lib2to3.
   - Many other removals
   <https://docs.python.org/3.13/whatsnew/3.13.html#removed> of deprecated
   classes, functions and methods in various standard library modules.
   - C API removals <https://docs.python.org/3.13/whatsnew/3.13.html#id10>
   and deprecations <https://docs.python.org/3.13/whatsnew/3.13.html#id9>.
   (Some removals present in alpha 1 were reverted in alpha 2, as the removals
   were deemed too disruptive at this time.)
   - New deprecations
   <https://docs.python.org/3.13/whatsnew/3.13.html#deprecated>, most of
   which are scheduled for removal from Python 3.15 or 3.16.

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

For more details on the changes to Python 3.13, see What’s new in Python
3.13 <https://docs.python.org/3.13/whatsnew/3.13.html>. The next
pre-release of Python 3.13 will be 3.13.0rc2, *the final release candidate*,
currently scheduled for 2024-09-03.
<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-more-resources-8>More
resources

   - Online Documentation <https://docs.python.org/3.13/>
   - PEP 719 <https://peps.python.org/pep-0719/>, 3.13 Release Schedule
   - Report bugs at Issues · python/cpython · GitHub
   <https://github.com/python/cpython/issues>.
   - Help fund Python directly
   <https://www.python.org/psf/donations/python-dev/> (or via GitHub
   Sponsors <https://github.com/sponsors/python>), and support the Python
   community <https://www.python.org/psf/donations/>.

<https://discuss.python.org/t/python-3-13-0-release-candidate-1-released/59703#p-181511-enjoy-the-new-releases-9>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
Łukasz Langa
Ned Deily
Steve Dower

--
Thomas Wouters <thomas@python.org>