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Python 3.8.0b3

Release Date: July 29, 2019

This is a beta preview of Python 3.8

Python 3.8 is still in development. This release, 3.8.0b3 is the third 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 3.8 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 (2019-09-30). Our goal is have no ABI changes after beta 3 and no code changes after 3.8.0rc1, the release candidate. To achieve that, it will be extremely important to get as much exposure for 3.8 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 3.8 series, compared to 3.7

Some of the new major new features and changes in Python 3.8 are:

  • PEP 572, Assignment expressions
  • PEP 570, Positional-only arguments
  • PEP 587, Python Initialization Configuration (improved embedding)
  • PEP 590, Vectorcall: a fast calling protocol for CPython
  • PEP 578, Runtime audit hooks
  • PEP 574, Pickle protocol 5 with out-of-band data
  • Typing-related: PEP 591 (Final qualifier), PEP 586 (Literal types), and PEP 589 (TypedDict)
  • Parallel filesystem cache for compiled bytecode
  • Debug builds share ABI as release builds
  • f-strings support a handy = specifier for debugging
  • continue is now legal in finally: blocks
  • on Windows, the default asyncio event loop is now ProactorEventLoop
  • on macOS, the spawn start method is now used by default in multiprocessing
  • multiprocessing can now use shared memory segments to avoid pickling costs between processes
  • typed_ast is merged back to CPython
  • LOAD_GLOBAL is now 40% faster
  • pickle now uses Protocol 4 by default, improving performance
  • (Hey, fellow core developer, if a feature you find important is missing from this list, let Ɓukasz know.)

There are many other interesting changes, please consult the "What's New" page in the documentation for a full list.

The next pre-release of Python 3.8 and the last beta will be 3.8.0b4, currently scheduled for 2019-08-26.

More resources

And now for something completely different

MINSTREL (singing): Brave Sir Robin ran away
MINSTREL: Bravely ran away away
ROBIN: I didn't!
MINSTREL: When danger reared its ugly head
MINSTREL: He bravely turned his tail and fled
MINSTREL: Yes, Brave Sir Robin turned about
ROBIN: I didn't!
MINSTREL: And gallantly he chickened out
MINSTREL: Bravely taking to his feet
ROBIN: I never did!
MINSTREL: He beat a very brave retreat
ROBIN: Oh, lie!
MINSTREL: Bravest of the brave
ROBIN: I never!

Full Changelog


Version Operating System Description MD5 Sum File Size GPG
Gzipped source tarball Source release 198611e0f36897e981a0de8601f1b063 23868827 SIG
XZ compressed source tarball Source release 19ce8bcfe90feb19e0883d37ca93ff04 17768608 SIG
macOS 64-bit installer Mac OS X for OS X 10.9 and later 4ddea5aefdfa939a1781b0fe5e66c3cc 28897151 SIG
Windows help file Windows 79a9eb8767e8f224936767ef8b1600d2 8427107 SIG
Windows x86-64 embeddable zip file Windows for AMD64/EM64T/x64 ffeddf54a66a6dc1c7099fba709d0671 8072054 SIG
Windows x86-64 executable installer Windows for AMD64/EM64T/x64 c1a4bd283e250a51c9002561ee7472a7 27405616 SIG
Windows x86-64 web-based installer Windows for AMD64/EM64T/x64 789c98e5e29b8a2bbfe4401d799f3434 1363232 SIG
Windows x86 embeddable zip file Windows 92ea635b66d2f039db740efbb435184a 7209732 SIG
Windows x86 executable installer Windows 28e1e20356a0ce1b7c34fc604c12f048 26315224 SIG
Windows x86 web-based installer Windows d613a6f6790cd1b9722ea5fc2dd2060f 1324736 SIG