> I think the OP's point was that it forces you to do all the number crunching via those extensions [...]
Almost. If you're using C extensions for performance, those extensions can release the GIL, and then you get parallelism in CPython. Although if you've got a bunch of small steps, Amdahl's law is going to bite you as each step needs to re-acquire the the GIL to proceed.
Note that for Numpy, I don't know which functions/methods actually bother to release the GIL, but it's possible in theory.
Almost. If you're using C extensions for performance, those extensions can release the GIL, and then you get parallelism in CPython. Although if you've got a bunch of small steps, Amdahl's law is going to bite you as each step needs to re-acquire the the GIL to proceed.
Note that for Numpy, I don't know which functions/methods actually bother to release the GIL, but it's possible in theory.