Free Threading and the Changing Semantics of the Python GIL: A Language Ecosystem at a Cross Road

Description

The Python community has two major players investing into the future of Python. Microsoft's Faster CPython team is pushing ahead with impressive performance improvements for the CPython interpreter, which has gotten at least 2x faster since Python 3.9 and they already have a baseline JIT compiler for CPython, too. At the same time, Meta is working hard on making free-threaded Python a reality and bring classic shared-memory multithreading to Python, without being limited by the still standard Global Interpreter Lock, which prevents true parallelism.

Both projects deliver major improvements to Python, and the wider ecosystem. So, it's all great, or is it?

In this talk, I'll discuss some of the aspects the Python core developers and wider community seem to not regard with the same urgency as I would hope for. Concurrency makes me scared, and I strongly believe the Python ecosystem should be scared, too, or look forward to the 2030s being "Python's Decade of Concurrency Bugs". We'll start out reviewing some of the changes in observable language semantics between Python 3.9 and today, discuss their implications, and because of course I have some old ideas lying around, try to propose a way fordward. In practice though, this isn't a small well-defined research project. So, I hope I can inspire some to follow down the rabbit hole of Python's free-threaded future.

Period	03 Apr 2025
Event title	Meeting of the IFIP Working Group 2.16 Pogramming Language Design
Event type	Workshop
Location	Serpiano, SwitzerlandShow on map
Degree of Recognition	International