[RELEASE] Python 3.13.0 beta 4 released.

Python 3.13.0b4, the final beta of Python 3.13, is now available:

https://www.python.org/downloads/release/python-3130b4/

*This is a beta preview of Python 3.13*

Python 3.13 is still in development. This release, 3.13.0b4, is the *final*
beta release preview of 3.13.

Beta release previews are intended to give the wider community the
opportunity to test new features and bug fixes and to prepare their
projects to support the new feature release.

We *strongly encourage* maintainers of third-party Python projects to *test
with 3.13* during the beta phase and report issues found to the Python bug
tracker <https://github.com/python/cpython/issues> as soon as possible.
While the release is planned to be feature complete entering the beta
phase, it is possible that features may be modified or, in rare cases,
deleted up until the start of the release candidate phase (Tuesday
2024-07-30). Our goal is to have *no ABI changes* after this final beta
release, and as few code changes as possible after 3.13.0rc1, the first
release candidate. To achieve that, it will be *extremely important* to get
as much exposure for 3.13 as possible during the beta phase.

Please keep in mind that this is a preview release and its use is *not*
recommended for production environments.
<https://discuss.python.org/t/python-3-13-0b4-now-available/58565#major-new-features-of-the-313-series-compared-to-312-1>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-3-13-0b4-now-available/58565#new-features-2>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).

<https://discuss.python.org/t/python-3-13-0b4-now-available/58565#typing-3>
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-3-13-0b4-now-available/58565#removals-and-new-deprecations-4>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 3.13.0rc1, *the first release candidate*,
currently scheduled for 2024-07-30.
<https://discuss.python.org/t/python-3-13-0b4-now-available/58565#more-resources-5>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 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-3-13-0b4-now-available/58565#enjoy-the-new-releases-6>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.

Finally, regards from a confusingly hot and rainy Munich,

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