[rguillebert]

You can use these C and Fortran routines on PyPy, just not with the CPython C extension API.

[takluyver]

There's a lot of established code built around the C API. It's not like it can just be rewritten using CFFI over a weekend.

[rguillebert]

Well, I'm not talking about every C extension in the world, I'm talking about thin bindings around C routines which is what numpy has for fft for example, someone wrote a basic equivalent for numpypy in a few hours with no prior numpypy/cffi knowledge.

[onalark]

Unfortunately, NumPy uses deep knowledge of the CPython API in quite a few places, which is one of the reasons implementing NumPyPy has been so challenging.

[rguillebert]

Another approach should be used for those, but to be clear I wasn't talking about the entire numpy library, I'm talking about things like numpy.fft