Python 3.13 Sees Last Minute Delay Due To Performance Regression

Python 3.13 had been scheduled for release today with a new interactive interpreter, experimental free-threaded build mode to disable the Global Interpreter Lock (GIL), an experimental JIT, and other shiny new features. But a performance regression has delayed the Python 3.13 release to next week and in turn an unexpected Python 3.13-rc3 final test release.

A "significant" performance regression in specific workloads held up the planned Python 3.13 release for 1 October. The regression is due to the incremental cyclic garbage collector introduced earlier this cycle. The change has now been reverted for Python 3.13 and will be revisited for Python 3.14. So there's Python 3.13-rc3 out today and should in effect be Python 3.13.0 barring any other last minute issues coming up in the next few days.

Python 3.13 is another big annual update for this popular programming language. Python 3.13 has a new interactive interpreter, removing the GIL in the experimental free-threaded build mode, an experimental JIT for faster performance, WASI is now a Tier-2 supported platform, and Android and iOS have been promoted to Tier-3 supported platforms.

Python 3.13 also adds support for type defaults in type parameters, a new type narrowing annotation, and other new annotations. More details on the unplanned Python 3.13-rc3 release and other changes to find with next week's Python 3.13 stable release can be found via the Python Insider Blog. If all goes well look for Python 3.13.0 stable to be christened next Monday.