Comment by mattip

Lots of questions :)

For c-extensions see https://www.pypy.org/posts/2018/09/inside-cpyext-why-emulati...

We would like to be able to "just JIT" better. But for that we need feedback about what is still unreasonably slow, and resources to work on improving it. Right now PyPy is on a shoe-string budget of volunteers.

For rust, like CPython, use PyO3, which works with PyPy.

I am not sure about Pydantic. Sounds like a topic for someone to investigate on their codebase and tell us how PyPy does.