This is a combined release of Python 3.8.5 and 3.9.0b5. Both are significant but for different reasons. Let’s dig in!
Security content in 3.8.5
We decided to release 3.8.5 ahead of schedule due to a number of security-related fixes. All details can be found in the change log https://docs.python.org/release/3.8.5/whatsnew/changelog.html#changelog but the gist is:
CVE-2019-20907 https://bugs.python.org/issue39017: infinite loop in a maliciously created .tar file BPO-41288 https://bugs.python.org/issue41288: segmentation fault during unpickling of objects using a crafted NEWOBJ_EX opcode BPO-39603 https://bugs.python.org/issue39603: HTTP headers could be injected through a maliciously crafter method parameter in http.client the original fix for CVE-2020-15801 caused a regression in 3.8.4 (see: BPO-41304 https://bugs.python.org/issue41304) A small number of other urgent regression fixes and quality-of-life improvements are also present in the release. Get the release here:
Maintenance releases for the 3.8 series will continue at the regular bi-monthly calendar, with 3.8.6 planned for mid-September 2020. The last beta of Python 3.9.0 now also available
Python 3.9 is still in development. This release, 3.9.0b5, is the last of five planned beta release previews. 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. You can get 3.9.0b5 here:
The next pre-release, the first release candidate of Python 3.9.0, will be 3.9.0rc1. It is currently scheduled for 2020-08-10. Call to action
We strongly encourage maintainers of third-party Python projects to test with 3.9 during the beta phase and report issues found to the Python bug tracker https://bugs.python.org/ 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 (2020-08-10). Our goal is have no ABI changes after beta 5 and as few code changes as possible after 3.9.0rc1, the first release candidate. To achieve that, it will be extremely important to get as much exposure for 3.9 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.
A reminder for core developers
To help make Python 3.9.0 the best possible release, our Development Cycle https://devguide.python.org/devcycle/#release-candidate-rc section of the Python Developer’s Guide documents that:
A branch preparing for an RC release can only have bugfixes applied that have been reviewed by other core developers. Generally, these issues must be severe enough (e.g. crashes) that they deserve fixing before the final release. All other issues should be deferred to the next development cycle, since stability is the strongest concern at this point.
You cannot skip the peer review during an RC, no matter how small! Even if it is a simple copy-and-paste change, everything requires peer review from a core developer.
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 https://www.python.org/dev/peps/pep-0584/, Union Operators in dict
PEP 585 https://www.python.org/dev/peps/pep-0585/, Type Hinting Generics In Standard Collections
PEP 593 https://www.python.org/dev/peps/pep-0593/, Flexible function and variable annotations
PEP 602 https://www.python.org/dev/peps/pep-0602/, Python adopts a stable annual release cadence
PEP 615 https://www.python.org/dev/peps/pep-0615/, Support for the IANA Time Zone Database in the Standard Library
PEP 616 https://www.python.org/dev/peps/pep-0616/, String methods to remove prefixes and suffixes
PEP 617 https://www.python.org/dev/peps/pep-0617/, New PEG parser for CPython
BPO 38379 https://bugs.python.org/issue38379, garbage collection does not block on resurrected objects;
BPO 38692 https://bugs.python.org/issue38692, os.pidfd_open added that allows process management without races and signals;
BPO 39926 https://bugs.python.org/issue39926, Unicode support updated to version 13.0.0;
BPO 1635741 https://bugs.python.org/issue1635741, 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 https://www.python.org/dev/peps/pep-0590 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 https://www.python.org/dev/peps/pep-0489/;
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 https://www.python.org/dev/peps/pep-0384/.
(Hey, fellow core developer, if a feature you find important is missing from this list, let Łukasz know mailto:firstname.lastname@example.org.)
We 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.