Python 3.8.0rc1

Release Date: Oct. 1, 2019

This is the release candidate of Python 3.8.0

This release, 3.8.0rc1, is the final planned release preview. Assuming no critical problems are found prior to 2019-10-14, the scheduled release date for 3.8.0, no code changes are planned between this release candidate and the final release.

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

specifier for debugging continue is now legal in finally: blocks

is now legal in blocks on Windows, the default asyncio event loop is now ProactorEventLoop

event loop is now 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

can now use shared memory segments to avoid pickling costs between processes typed_ast is merged back to CPython

is merged back to CPython LOAD_GLOBAL is now 40% faster

is now 40% faster pickle now uses Protocol 4 by default, improving performance

now uses Protocol 4 by default, improving performance (Hey, fellow core developer, if a feature you find important is missing from this list, let Łukasz know.)

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

More resources

And now for something completely different

WISE MAN #1: We are three wise men.

MANDY: Well, what are you doing creeping around a cow shed at two o'clock in the morning? That doesn't sound very wise to me.

WISE MAN #3: We are astrologers.

WISE MAN #1: We have come from the East.

MANDY: Is this some kind of joke?

WISE MAN #2: We wish to praise the infant.

WISE MAN #1: We must pay homage to him.

MANDY: Homage? You're all drunk. It's disgusting. Out! The lot, out!

Full Changelog