Python 3.9.0

Release date: Oct. 5, 2020

This is the stable release of Python 3.9.0

Note: The release you're looking at is Python 3.9.0, a legacy release. Python 3.11 is now the latest feature release series of Python 3. Get the latest release of 3.11.x here.

Installer news

This is the first version of Python to default to the 64-bit installer on Windows. The installer now also actively disallows installation on Windows 7. Python 3.9 is incompatible with this unsupported version of Windows.

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 573, Module State Access from C Extension Methods
• 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 614, Relaxing Grammar Restrictions On Decorators
• PEP 615, Support for the IANA Time Zone Database in the Standard Library
• 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.

You can find a more comprehensive list in this release's "What's New" document.

More resources

• Online Documentation
• PEP 596, 3.9 Release Schedule
• Report bugs at https://bugs.python.org.
• Help fund Python and its community.

And now for something completely different

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Mr. Simpson: how'd'y'do.
Wapcaplet: Now, Mr. Simpson... Now, I understand you want us to advertise your washing powder.
S: String.
W: String, washing powder, what's the difference. We can sell anything.
S: Good. Well I have this large quantity of string, a hundred and twenty-two thousand miles of it to be exact, which I inherited, and I thought if I advertised it...
W: Of course! A national campaign. Useful stuff, string, no trouble there.
S: Ah, but there's a snag, you see. Due to bad planning, the hundred and twenty-two thousand miles is in three inch lengths. So it's not very useful.
W: Well, that's our selling point! 'SIMPSON'S INDIVIDUAL STRINGETTES!'
S: What?
W: 'THE NOW STRING! READY CUT, EASY TO HANDLE, SIMPSON'S INDIVIDUAL EMPEROR STRINGETTES - JUST THE RIGHT LENGTH!'
S: For what?
W: 'A MILLION HOUSEHOLD USES!'
S: Such as?
W: Uhmm...Tying up very small parcels, attatching notes to pigeons' legs, uh, destroying household pests...
S: Destroying household pests?! How?
W: Well, if they're bigger than a mouse, you can strangle them with it, and if they're smaller than, you flog them to death with it!
S: Well surely!....
W: 'DESTROY NINETY-NINE PERCENT OF KNOWN HOUSEHOLD PESTS WITH PRE-SLICED, RUSTPROOF, EASY-TO-HANDLE, LOW CALORIE SIMPSON'S INDIVIDUAL EMPEROR STRINGETTES, FREE FROM ARTIFICIAL COLORING, AS USED IN HOSPITALS!'

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