[scruple]

That's very interesting, thank you for the link. I've used Python since the 00s and I don't ever recall having come across sub-interpreters...

[Znafon]

They were always usable using the C-API but not exposed to the Python library (and until 3.12 you were blocked by the shared GIL so there was little point anyway).

Now that the work from Eric Snow has been merged, you can use https://pypi.org/project/interpreters-3-12/ to create one from Python code.