Python Using C Modules

[Sinkingships7]

I've googled a bit, and found quite a few tutorials on writing C modules to use in Python code. However, I don't find any of these tutorials to be straight-forward enough for my purposes. For now, I just want the basics. Just for practice, I want to write a C module containing a function to print "hello" on the screen, and call it using Python.

Can someone give a simple example of how this is done?

[pmasiar]

Wybiral is not around for quite a while - hopefully he has more productive way to spend his time :-) Try to PM him. I believe he did it.

[Rich78]

This looks like it could cover what you're looking for.

http://www.python.org/doc/2.5.2/ext/simpleExample.html

You could pass any system command through it from Python.

Python:


>>> import spam
>>> status = spam.system("echo hello world")


C:


#include <Python.h>
static PyObject *
spam_system(PyObject *self, PyObject *args)
{
const char *command;
int sts;

if (!PyArg_ParseTuple(args, "s", &command))
return NULL;
sts = system(command);
return Py_BuildValue("i", sts);
}

[snova]

This is what I figured out from five minutes in the API docs:

helloutils.c:



#include <Python.h>

static PyObject* helloutils_output( PyObject* self, PyObject* args )
{
printf( "Hello!\n" );
Py_RETURN_NONE;
}

static PyMethodDef HelloutilsMethods[] =
{
{ "output", helloutils_output, METH_VARARGS, "Prints \"Hello!\\n\"." },
{ NULL, NULL, 0, NULL }
};

PyMODINIT_FUNC inithelloutils()
{
PyObject* module = Py_InitModule( "helloutils", HelloutilsMethods );
}


Compile:


gcc -fPIC helloutils.c -o helloutils.so -I/usr/include/python2.5 -shared

Example:



>>> import helloutils
>>> helloutils.output()
Hello!
>>>


The C code was mostly copied from the documentation.