SWIG:Examples:python:simple

SWIG/Examples/python/simple/

Simple Python Example

This example illustrates how you can hook Python to a very simple C program containing a function and a global variable.

The C Code

Suppose you have the following C code:

/* File : example.c */

/* A global variable */
double Foo = 3.0;

/* Compute the greatest common divisor of positive integers */
int gcd(int x, int y) {
  int g;
  g = y;
  while (x > 0) {
    g = x;
    x = y % x;
    y = g;
  }
  return g;
}

The SWIG interface

Here is a simple SWIG interface file:

/* File: example.i */
%module example

extern int gcd(int x, int y);
extern double Foo;

Compilation

swig -python example.i
Compile example_wrap.c and example.c to create the extension examplemodule.so.

Using the extension

Click here to see a script that calls our C functions from Python.

Key points

Use the import statement to load your extension module from Python. For example:
```
import example
```
C functions work just like Python functions. For example:
```
g = example.gcd(42,105)
```
C global variables are accessed through a special variable called 'cvar'. For example:
```
a = example.cvar.Foo
```