Simon Willison’s Weblog

15th May 2023 - Link Blog

Real Multithreading is Coming to Python - Learn How You Can Use It Now (via) Martin Heinz provides a detailed tutorial on trying out the new Per-Interpreter GIL feature that’s landing in Python 3.12, which allows Python code to run concurrently in multiple threads by spawning separate sub-interpreters, each with their own dedicated GIL.

It’s not an easy feature to play with yet! First you need to compile Python yourself, and then use APIs that are generally only available to C code (but should hopefully become available to Python code itself in Python 3.13).

Martin’s workaround for this is ingenious: it turns out the Python test.support package provides utility functions to help write tests against interpreters, and Martin shows how to abuse this module to launch, run and cleanup interpreters using regular Python code.

He also demonstrates test.support.interpreters.create_channel(), which can be used to create channels with receiver and sender ends, somewhat similar to Go.