Swig Tutorial example Mac Os Lion

This tutorial is based on Leopard Tutorial but still works, thou some warnings.

First, we create an example.c file with this content:

/* File : example.c */

#include <time.h>
double My_variable = 10.0;

int fact(int n) {
    if (n <= 1) return 1;
    else return n*fact(n-1);
}

int my_mod(int x, int y) {
    return (x%y);
}

char *get_time()
{
    time_t ltime;
    time(&ltime);
    return ctime(&ltime);
}

Second, we create the interface between C and Python with the following file:

/* example.i */
%module example
%{
    /* Put header files here or function declarations like below */
    extern double My_variable;
    extern int fact(int n);
    extern int my_mod(int x, int y);
    extern char *get_time();
%}

extern double My_variable;
extern int fact(int n);
extern int my_mod(int x, int y);
extern char *get_time();

Now that we have all the source files we need, we compile them in this way:

$ swig -python example.i
$ cc -c `python-config --cflags` example.c example_wrap.c
$ cc -bundle `python-config --ldflags` example.o example_wrap.o -o _example.so

if you have problems with this step check this other post

So, everything looks nice, but how do we use the dynamic module in python?

>>> import example
>>> example
<module 'example' from 'example.pyc'>
>>> example.cvar.My_variable
10.0
>>> example.my_mod(20,10)
0
>>> example.fact(14)
1278945280
>>> example.get_time()
'Sat Feb 11 19:27:05 2012\n'

disclaimer: this is just the tutorial from the swig's homepage, it only shows how you can actually use some C power into python. For example, scipy package, in the module cluster uses a C function wrapped into python code.