PYTHON setup.py build_ext --inplace

############# setup.py #############

from Cython.Build.Dependencies import cythonize
from distutils.core import setup

setup(
    ext_modules = cythonize(["a.pyx", "b.pyx", "include_both.pyx"]),
    )

############# a.pyx ###############

cdef public f():
    pass
    
############# b.pyx ###############

cdef public g():
    pass
    
############# include_both.pyx ####

# This is just checking that a and b don't duplicate any names
# and thus it's possible to include them both in one place

cdef extern from "a.h":
    pass
    
cdef extern from "b.h":
    pass