There are several other options. The extension can be written as a pure C extension, with CFFI for the bindings, and code in Python to present the public API. O

There are several other options. The extension can be written as a pure C extension, with CFFI for the bindings, and code in Python to present the public API. Or write the extension in Cython, which has backends for both CPython and PyPy's cpyext (I have no experience with this option).