Python 3.9

Python 3.9 is available. What’s new:

New syntax features:

• PEP 584, union operators added to dict;
• PEP 585, type hinting generics in standard collections;
• PEP 614, relaxed grammar restrictions on decorators.

New built-in features:

• PEP 616, string methods to remove prefixes and suffixes.

New features in the standard library:

• PEP 593, flexible function and variable annotations;
• os.pidfd_open() added that allows process management without races and signals.

Interpreter improvements:

• PEP 573, fast access to module state from methods of C extension types;
• PEP 617, CPython now uses a new parser based on PEG;
• a number of Python builtins (range, tuple, set, frozenset, list, dict) are now sped up using PEP 590 vectorcall;
• garbage collection does not block on resurrected objects;
• a number of Python modules (_abc, audioop, _bz2, _codecs, _contextvars, _crypt, _functools, _json, _locale, math, 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.

New library modules:

• PEP 615, the IANA Time Zone Database is now present in the standard library in the zoneinfo module;
• an implementation of a topological sort of a graph is now provided in the new graphlib module.

Release process changes:

• PEP 602, CPython adopts an annual release cycle.