Python 3.15.0a4

Release date: Jan. 13, 2026

This is an early developer preview of Python 3.15

Major new features of the 3.15 series, compared to 3.14

Python 3.15 is still in development. This release, 3.15.0a4, is the fourth of seven planned alpha releases.

Alpha releases are intended to make it easier to test the current state of new features and bug fixes and to test the release process.

During the alpha phase, features may be added up until the start of the beta phase (2026-05-05) and, if necessary, may be modified or deleted up until the release candidate phase (2026-07-28). Please keep in mind that this is a preview release and its use is not recommended for production environments.

Many new features for Python 3.15 are still being planned and written. Among the new major new features and changes so far:

• PEP 799: A new high-frequency, low-overhead, statistical sampling profiler and dedicated profiling package
• PEP 686: Python now uses UTF-8 as the default encoding
• PEP 782: A new PyBytesWriter C API to create a Python bytes object
• The JIT compiler has been significantly upgraded, with 3-4% geometric mean performance improvement on x86-64 Linux over the standard interpreter, and 7-8% speedup on AArch64 macOS over the tail-calling interpreter
• Improved error messages
• (Hey, fellow core developer, if a feature you find important is missing from this list, let Hugo know.)

The next pre-release of Python 3.15 will be 3.15.0a5, currently scheduled for 2026-02-10.

More resources

• Online documentation
• PEP 790, 3.15 release schedule
• Report bugs at https://github.com/python/cpython/issues
• Help fund Python directly (or via GitHub Sponsors) and support the Python community

And now for something completely different

Upon this every soul was confounded; for the phenomenon just then observed by Ahab had unaccountably escaped every one else; but its very blinding palpableness must have been the cause.

Thrusting his head half way into the binnacle, Ahab caught one glimpse of the compasses; his uplifted arm slowly fell; for a moment he almost seemed to stagger. Standing behind him Starbuck looked, and lo! the two compasses pointed East, and the Pequod was as infallibly going West.

But ere the first wild alarm could get out abroad among the crew, the old man with a rigid laugh exclaimed, “I have it! It has happened before. Mr. Starbuck, last night’s thunder turned our compasses—that’s all. Thou hast before now heard of such a thing, I take it.”

“Aye; but never before has it happened to me, sir,” said the pale mate, gloomily.

Enjoy the new release

Thanks to all of the many volunteers who help make Python Development and these releases possible! Please consider supporting our efforts by volunteering yourself or through organisation contributions to the Python Software Foundation.

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