Python 3.9.0b1 is now available for testing

On behalf of the entire Python development community, and the currently
serving Python release team in particular, I’m pleased to announce the
release of Python 3.9.0b1. Get it here:

https://www.python.org/downloads/release/python-390b1/

This is a beta preview of Python 3.9

Python 3.9 is still in development. This release, 3.9.0b1, is the first of four 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.

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
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 4 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.

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 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.

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

The next pre-release, the second beta release of Python 3.9, will be 3.9.0b2. It is currently scheduled for 2020-06-08.