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To: python-list@python.org
From: Stefan Behnel <stefan_ml@behnel.de>
Subject: Re: Building an extension module with SWIG
Date: Sat, 30 May 2015 21:05:39 +0200
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garyr schrieb am 30.05.2015 um 18:22:
> I'm trying to create an extension module using SWIG. I've
> succeeded in generating a pyd file but when I import the module I get the
> error message: "SystemError: dynamic module not initialized properly." I
> added an initfoo() function but that didn't solve the problem. Below are the
> various files, a slightly modified version of a SWIG exmaple.
> I'm using Python 2.7
> 
> What am I missing?
> 
> //foo.c:
> #include "foo.h"
> double Foo;
> void initfoo()
> {
>     Foo = 3.0;
> }

This is wrong and you also won't need that.


> int gcd(int x, int y) {
>   int g;
>   g = y;
>   while (x > 0) {
>     g = x;
>     x = y % x;
>     y = g;
>   }
>   return g;
> }
> [...]

Just in case you're not bound to SWIG yet, here's a Cython [1] version of
your code:

    # put this in a file called "foo.pyx"

    def gcd(int x, int y):
        while x > 0:
            y, x = x, y % x
        return y

Compile it ("cythonize -b foo.pyx") and you'll get an extension module that
executes faster than what SWIG would give you and keeps everything in one
file to improve readability.

Stefan


[1] http://cython.org/