I was actually considering the other day that I was surprised Cython (and numba?) don't do something where they use a copy of the libpython source to allow them

I was actually considering the other day that I was surprised Cython (and numba?) don't do something where they use a copy of the libpython source to allow them to inline calls back into python-land. Yes, fraught with packaging/distribution difficulties, but possibly worth it for situations where the speedup is needed.