Load shared object using ctyped.cdll.loadLibrary from dist-packages folder

I created this setup.py to compile a libDIV.so shared library and install it.

from distutils.core import setup, Extension

libDIV = Extension(
  'DIV',
  sources = ['example.c']
)

setup (
  name="divv",
  version = '0.1',
  description = 'DIVV, you want it',
  ext_modules = [libDIV],
  packages = [''],
  package_data={'': ['libDIV.so']}
)

After running python3 setup.py install, the shared library is placed in the dist-packages folder as:

/usr/local/lib/python3.4/dist-packages/DIV.cpython-34m.so

In an extra file example.py I want to load the library using ctypes.cdll.LoadLibrary, such that example.py can wrap it’s functionality in more elegant, type checked python functions.

import ctypes
lib = ctypes.cdll.LoadLibrary('DIV.so') # not sure what to do here

def divide_modulo(a, b):
  div = ctypes.c_int(0)
  rest = ctypes.c_int(0)
  lib.divide_modulo(a, b, ctypes.byref(div), ctypes.byref(rest))
  return (div.value, rest.value)

print(divide_modulo(11, 4))

class DynamicArray(ctypes.Structure):
  _fields_ = [("n", ctypes.c_int), ("r", ctypes.POINTER(ctypes.c_int))]

However I’m not sure how to pass the right file name and location for the created shared object file.

How should I distribute / configure setup.py for a library of c-files which build into a shared library and some python code to wrap the c-functionality?

For completeness, this is example.c:

#include <stdlib.h>

void divide_modulo(int a, int b, int *div, int *rest)
{
*div  = a / b;
*rest = a % b;
}

typedef struct dynamic_array {
  int n;
  int *r;
} dynamic_array;

dynamic_array return_dynamic_array(int n)
{
  dynamic_array r;
  r.n = n;
  r.r = (int *)malloc(sizeof(int) * n);
  unsigned int i = 0;
  for (; i < n; ++i)
  r.r[i] = i;
  return r;
}

EDIT:

Currently I do this to find the file name:

import ctypes, numpy, site, os.path
from scipy.sparse import csr_matrix

so_file = next(
    os.path.join(directory, filename)
    for directory in site.getsitepackages()
    for filename in os.listdir(directory)
    if filename.startswith("DIV.") and filename.endswith(".so")
)
lib = ctypes.cdll.LoadLibrary(so_file)

But honestly, this is quite smelly. I’m not sure the file will always be called DIV.something.so and that vice versa that other files are not named like this.

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