python - Cython: ImportError: No module named 'myModule': how to call a cython module containing a cimport to another cython nodule?

Question

I'm trying to import a cython module data.pyx into another cython module user.pyx. Everything compile fine, but when I try to call user.pyx in a python module, I am getting the error 'ImportError: No module named data'.

Everything is in the same directory.

package/
    __init__.py   #empty
    setup.py      
    data.pxd
    data.pyx
    user.pyx

My setup.py

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext


ext_modules = [
    Extension("data", ["data.pyx"]),
    Extension("user", ["user.pyx"],include_dirs = ['myPackageDir'])
    ]

setup(
  name = 'app',
  cmdclass = {'build_ext': build_ext},
  ext_modules = ext_modules  
)

Running the following test.py will raised the error.

import user     #this line raised the 'ImportError: No module named data' below
user.doSomething()

The exception I get is

Traceback:
 File "test.py", line 1, in <module>
    import package.user
  File "user.pyx", line 1, in init user (user.c:3384)
ImportError: No module named data

How can I make the import work? Thanks for any help.

Answer 1

I encounter this problem again in an another project. To solve it, here is what I did:

• all import and cimport statement must be fully qualified
• all the python code must be contained in a rootFolder
• the setup.py must be at the same level than the rootFolder
• all folder in the rooFolder including the rootFolder must contains a __init__.py
• in your setup.py the extension's include_dirs must contains '.'

I created a simple project which illustrates this here.
This page helped me created it.
But my project is simpler and I think it would have helped me a lot if I had it.
My project also illustrate how to automatically build all cython files in a project.