On the other hand, there are many C extensions which are just interop/wrappers for existing C code. I think no language is naive enough to think they can get away without C interop.

C extensions are actually pretty nice because you can wrap the C code into idiomatic Python. With ctypes, you have to e.g. maintain two structure definitions, which is very problematic for some codebases.

> In following PyPy (and other alternate Python discussions) it seems like eliminating the GIL and getting better performance out of Python, even in C, isn't that hard if you drop the C extensions.

AFAIK, many projects initially struggle to even achieve performance parity with CPython. The GIL isn't evil, it's a simple solution to a hard problem. But at this point, a complex solution to a hard problem is better if it's faster, and some people care more about speed than C interop (and vice versa).

What would be awesome is a Python runtime that could run with fine-grain locking until a C extension is loaded, and then continue with coarse locking. But the problem is still there's no upgrade path for C interop.

The only thing I can think of is using type annotations and something like Cython's cdef to write Python-implementation-independent C interop that doesn't suck as bad as ctypes. Then the Python rumtime could also lock the arguments at a very fine level while the function is being called.