import cffi ffi = cffi.FFI() ffi.embedding_api(""" int add(int, int); """) ffi.embedding_init_code(""" from _embedding_cffi import ffi print("preparing") # printed once @ffi.def_extern() def add(x, y): print("adding %d and %d" % (x, y)) return x + y """) ffi.set_source("_embedding_cffi", "") ffi.compile(verbose=True)