Create and use a shared library using Python's ctypes module

compile.sh

# Compile a shared library
gcc -shared -o libmean.so.1 mean.c

mean.c

#include "mean.h"

double mean(double a, double b) {
  return (a+b)/2;
}

mean.h

// Returns the mean of passed parameters
double mean(double, double);

test_libmean.py

>>> import ctypes
>>> libmean = ctypes.CDLL("libmean.so.1") # loads the shared library
>>> libmean.mean.restype = ctypes.c_double # define mean function return type
>>> libmean.mean(ctypes.c_double(10), ctypes.c_double(3)) # call mean function needs cast arg types
6.5
>>> libmean.mean.argtypes = [ctypes.c_double, ctypes.c_double] # define arguments types
>>> libmean.mean(10, 3) # call mean function does not need cast arg types
6.5
>>> type(libmean.mean(10, 5)) # returned value is converted to python types
<type 'float'>