Cython example of multiple pyx files

a.pyx

cdef int _fib(int n):
    cdef int i
    cdef int a=0, b=1
    for i in range(n):
        a, b = a + b,a
    return a

def fib(n):
    return _fib(n)

b.pyx

import a

def caller(n):
    return a.fib(n)

setup.py

from distutils.core import setup
from Cython.Build import cythonize
setup(ext_modules=cythonize('./*.pyx'))

Run:
python3 setup.py build_ext --inplace
Test in ipython or python shell like:

>>> import a, b
>>> a.fib(10)
55
>>> b.caller(10)
55