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Python 3.9.0rc2

Release Date: Sept. 17, 2020

This is the second release candidate of Python 3.9

This release, 3.9.0rc2, is the last preview before the final release of Python 3.9.0 on 2020-10-05. In the mean time, we strongly encourage maintainers of third-party Python projects to prepare their projects for 3.9 compatibility during this phase. As always, report any issues to the Python bug tracker.

Please keep in mind that this is a preview release and its use is not recommended for production environments.

Information for core developers

The 3.9 branch is now accepting changes for 3.9.1. To maximize stability, the final release will be cut from the v3.9.0rc2 tag. If you need the release manager to cherry-pick any critical fixes, mark issues as release blockers and/or add him as a reviewer on a critical backport PR on GitHub.

To see which changes are currently cherry-picked for inclusion in 3.9.0, look at the short-lived branch-v3.9.0 on GitHub.

Installer news

This is the first version of Python to default to the 64-bit installer on Windows. The installer now also actively disallows installation on Windows 7. Python 3.9 is incompatible with this unsupported version of Windows.

Major new features of the 3.9 series, compared to 3.8

Some of the new major new features and changes in Python 3.9 are:

  • PEP 584, Union Operators in dict
  • PEP 585, Type Hinting Generics In Standard Collections
  • PEP 593, Flexible function and variable annotations
  • PEP 602, Python adopts a stable annual release cadence
  • PEP 615, Support for the IANA Time Zone Database in the Standard Library
  • PEP 616, String methods to remove prefixes and suffixes
  • PEP 617, New PEG parser for CPython
  • BPO 38379, garbage collection does not block on resurrected objects;
  • BPO 38692, os.pidfd_open added that allows process management without races and signals;
  • BPO 39926, Unicode support updated to version 13.0.0;
  • BPO 1635741, when Python is initialized multiple times in the same process, it does not leak memory anymore;
  • A number of Python builtins (range, tuple, set, frozenset, list, dict) are now sped up using PEP 590 vectorcall;
  • A number of Python modules (_abc, audioop, _bz2, _codecs, _contextvars, _crypt, _functools, _json, _locale, operator, resource, time, _weakref) now use multiphase initialization as defined by PEP 489;
  • A number of standard library modules (audioop, ast, grp, _hashlib, pwd, _posixsubprocess, random, select, struct, termios, zlib) are now using the stable ABI defined by PEP 384.

More resources

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(Cut to a man sitting at usual desk.)

Boniface (Michael Palin): Good evening. Tonight on 'It's the Mind', we examine the phenomenon of déjà vu. That strange feeling we sometimes get that we've lived through something before, that what is happening now has already happened tonight.
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(Cut to opening title sequence with montage of psychiatric photos and music.)
(Cut back to Mr Boniface at desk, shaken.)


Boniface: Good evening. Tonight on 'It's the Mind' we examine the phenomenon of déjà vu, that strange feeling we someti... (looks around) ...mes get... (looks increasingly worried) that... we've lived through something...

Full Changelog


Version Operating System Description MD5 Sum File Size GPG
Gzipped source tarball Source release 4b5bc3114875aad8b2ffc88a3d564ce1 24.1 MB SIG
XZ compressed source tarball Source release 3e34e48b479f4beec2c0c80fdbde52a2 17.9 MB SIG
macOS 64-bit installer macOS for OS X 10.9 and later cec408a09e67431790c749b9036aa4f9 28.3 MB SIG
Windows help file Windows 05705e64e58d90636f6e72391228753c 8.3 MB SIG
Windows x86 embeddable zip file Windows a10efb536c66e82f1e14aff9506eaf84 7.2 MB SIG
Windows x86 executable installer Windows 2685aa038fa2cfd8121fa32da18ef5ca 25.7 MB SIG
Windows x86 web-based installer Windows 322fe6c122d6c1f27ab62b14086b351b 1.3 MB SIG
Windows x86-64 embeddable zip file Windows for AMD64/EM64T/x64 33ab676ef4db4f8ec6411a0a43a8f095 8.0 MB SIG
Windows x86-64 executable installer Windows for AMD64/EM64T/x64 9f96f0e9c131609d2e7146d66ede7541 26.8 MB SIG
Windows x86-64 web-based installer Windows for AMD64/EM64T/x64 c6568b657f4b7d2ac9ed83365b5f6b16 1.3 MB SIG