How to put my Python C-module inside package?

Question

I would like to gather multiple Python modules under one package, so they do not reserve too many names from global set of python packages and modules. But I have problems with modules that are written in C.

Here is a very simple example, straight from the official Python documentation. You can find it at the bottom of the page from here: http://docs.python.org/distutils/examples.html

from distutils.core import setup
from distutils.extension import Extension
setup(name='foobar',
      version='1.0',
      ext_modules=[Extension('foopkg.foo', ['foo.c'])],
      )

My foo.c file looks like this

#include <Python.h>

static PyObject *
foo_bar(PyObject *self, PyObject *args);

static PyMethodDef FooMethods[] = {
    {
        "bar",
        foo_bar,
        METH_VARARGS,
        ""
    },
    {NULL, NULL, 0, NULL}
};

static PyObject *
foo_bar(PyObject *self, PyObject *args)
{
    return Py_BuildValue("s", "foobar");
}

PyMODINIT_FUNC
initfoo(void)
{
    (void)Py_InitModule("foo", FooMethods);
}

int
main(int argc, char *argv[])
{
    // Pass argv[0] to the Python interpreter
    Py_SetProgramName(argv[0]);

    // Initialize the Python interpreter.  Required.
    Py_Initialize();

    // Add a static module
    initfoo();

    return 0;
}

It builds and installs fine, but I cannot import foopkg.foo! If I rename it to just "foo" it works perfectly.

Any ideas how I can make the "foopkg.foo" work? For example changing "foo" from Py_InitModule() in C code to "foopkg.foo" does not help.

Janne Karila · Accepted Answer · 2012-10-12 10:49:33Z

6

There must be an __init__.py file in the foopkg folder, otherwise Python does not recognize as a package.

Create a foopkg folder where setup.py is, and put an empty file __init__.py there, and add a packages line to setup.py:

from distutils.core import setup
from distutils.extension import Extension
setup(name='foobar',
      version='1.0',
      packages=['foopkg'],
      ext_modules=[Extension('foopkg.foo', ['foo.c'])],
      )

edited Oct 12, 2012 at 10:49

answered Oct 12, 2012 at 10:44

Janne Karila

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1 Comment

Henrik Heino Over a year ago

That did the trick! Thanks :) Although I still think that should have been mentioned in the Python docs :/

T.H. · Accepted Answer · 2021-05-30 08:18:29Z

1

distutils will be deprecated since python 3.10 , instead you can use setuptools, which is an enhanced alternative of distutils , so you don't need to pass packages argument in your setup(). For example :

from setuptools import setup, Extension
setup(name='foobar',
      version='1.0',
      ext_modules=[Extension('foopkg.foo', ['foo.c'])],
      )

Then build and install your C extension

python /PATH/TO/setup.py install

After building your C extension successfully, test whether it can be imported as expected by running this command:

python -c "from foopkg import foo"

[side note] One more thing about setuptool is that you can uninstall the C extension package by simply running pip uninstall, for example : python -m pip uninstall foobar

edited May 30, 2021 at 8:18

answered May 30, 2021 at 8:11

T.H.

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