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Python 3.8.0b1

Release Date: June 4, 2019

This is a beta preview of Python 3.8

Python 3.8 is still in development. This release, 3.8.0b1 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 3.8 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 will be 3.8.0b2, currently scheduled for 2019-07-01.

More resources

And now for something completely different

Eric: Who'd a thought thirty years ago we'd all be sittin' here drinking Chateau de Chassilier wine?
Michael: Aye. In them days, we'd a' been glad to have the price of a cup o' tea.
Graham: A cup ' COLD tea.
Eric: Without milk or sugar.
Terry: OR tea!
Michael: In a filthy, cracked cup.
Eric: We never used to have a cup. We used to have to drink out of a rolled up newspaper.
Graham: The best WE could manage was to suck on a piece of damp cloth.
...
Michael: But you try and tell the young people today that... and they won't believe ya'.
ALL: Nope, nope...

Full Changelog

Files

Version Operating System Description MD5 Sum File Size GPG
Gzipped source tarball Source release aff74abe251159e87b8f8c146840c350 23690287 SIG
XZ compressed source tarball Source release 0540e00104a96e0e2f8cbcc8488e9895 17601532 SIG
macOS 64-bit installer Mac OS X for OS X 10.9 and later 773621ed6782685824fe90d06f126611 28484798 SIG
Windows help file Windows 7af6a88167779c0bdb769367360b703e 8338785 SIG
Windows x86-64 embeddable zip file Windows for AMD64/EM64T/x64 6f209dd58054ff0ed60b3f33c6045b37 7673842 SIG
Windows x86-64 executable installer Windows for AMD64/EM64T/x64 cded61ef6def13e17291dd7af8286322 27155472 SIG
Windows x86-64 web-based installer Windows for AMD64/EM64T/x64 45a678ff4dfe66c2f8efa026a5951d57 1363184 SIG
Windows x86 embeddable zip file Windows bab84a9d5ebd6c6915f5f84b567dd9bd 6936172 SIG
Windows x86 executable installer Windows 670d149c68aa36438f484f82a7832ed1 26156352 SIG
Windows x86 web-based installer Windows 22cae5681e67257324218be48e85b92d 1324880 SIG