Python 3.15 Alpha 6 Drops with JIT Speed Boost and New Profiler

Python 3.15 Alpha 6 Released: JIT Compiler Gets Major Speed Boost, New Profiler Introduced

The Python Software Foundation today announced the availability of Python 3.15.0 alpha 6, the sixth of eight planned alpha releases for the upcoming Python 3.15 series. This developer preview already delivers up to 8% faster execution on some platforms thanks to a significantly upgraded just-in-time (JIT) compiler, along with a new statistical profiler and other features.

"This is an early developer preview intended to make it easier to test the current state of new features and bug fixes," said release manager Hugo van Kemenade. "While production use is not recommended, we encourage developers to try it and report issues."

Key New Features in Python 3.15.0a6

• PEP 799: A high-frequency, low-overhead statistical sampling profiler and dedicated profiling package.
• PEP 798: Unpacking in comprehensions with * and **.
• PEP 686: UTF-8 is now the default encoding.
• PEP 782: New PyBytesWriter C API for creating Python bytes objects.
• PEP 728: TypedDict with typed extra items.
• JIT Compiler Upgrades: 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

Background

Python 3.15 is still under active development. The alpha phase allows new features to be added, modified, or even removed before the beta phase begins on May 5, 2026. The first release candidate is scheduled for July 28, 2026. The next pre-release, 3.15.0a7, is expected on March 10, 2026.

Developers can download the alpha 6 preview from the official Python downloads page.

What This Means

This alpha release gives early adopters and library maintainers a chance to test new features—especially the JIT improvements—before the final release. The new profiler (PEP 799) should help optimize Python applications with minimal overhead. The UTF-8 default encoding (PEP 686) simplifies cross-platform text handling, while byte-oriented C code can benefit from PyBytesWriter (PEP 782).

"We strongly advise against using this in production," van Kemenade added. "But if you're building tools or libraries for 3.15, now is the time to start testing."

How to Help

Report bugs via the CPython issue tracker. Financial support can be provided through the Python Software Foundation or GitHub Sponsors.

The release team—Hugo van Kemenade, Ned Deily, Steve Dower, and Łukasz Langa—expressed gratitude to all volunteers. "Consider volunteering or contributing through your organization," they said in a statement.