Reposting the reply I put on the steering council pep 703 decision issue here per Guido’s suggestion just so it’s all in one place:
“”"The steering council is going to take its time on this. A huge thank you for working to keep it up to date! We’re not ready to simply pronounce on 703 as it has a HUGE blast radius.
Software isn’t ready for the decades of Python assumptions such a change turns on its head, even when it appears to work fine it’s a statistical qualm of “but does it really? how do we actually know? when might it not and how often?” asked for every transitive dep of code. For some things that Q&A could be easy, but for others it becomes a can of worms.
From a steering council perspective we effectively view a 703 threading enabled interpreter at a high level as a fork of the CPython VM. In the sense that extension modules are unlikely to work without noteworthy modifications and even some pure Python libraries may even need to start considering locking where it had not in the past.
That does not mean “no” to this. There is demand for it. (personally, I’ve wanted this since forever!) It’s just that it won’t be easy and we’ll need to consider the entire ecosystem and how to smoothly allow such a change to happen without breaking the world.
I’m glad to see the continued discuss thread with faster-cpython folks in particular piping up. The intersection between this work and ongoing single threaded performance improvements will always be high and we don’t want to hamper that in the near term.“”"
– me with a steering council hat on