Best way to call C-functions from python?

Question

I've written a high level motor controller in Python, and have got to a point where I want to go a little lower level to get some speed, so I'm interested in coding those bits in C.

I don't have much experience with C, but the math I'm working on is pretty straightforward, so I'm sure I can implement with a minimal amount of banging my head against the wall. What I'm not sure about is how best to invoke this compiled C program in order to pipe it's outputs back into my high-level python controller.

I've used a little bit of ctypes, but only to pull some functions from a manufacfturer-supplied DLL...not sure if that is an appropriate path to go down in this case.

Any thoughts?

Seems similar to http://stackoverflow.com/questions/145270/calling-c-c-from-python — Shafik Yaghmour, Apr 16 '13 at 02:48
You may also want to have a look at Cython. It's built for pretty much exactly this purpose and you may not even have to change your code very much. — FatalError, Apr 16 '13 at 02:50

score 2 · Accepted Answer · answered Apr 16 '13 at 03:11

You can take a look at this tutorial here.

Also, a more reliable example on the official python website, here.

For example,

sum.h function

int sum(int a, int b)

A file named, module.c,

#include <Python.h>
#include "sum.h"

static PyObject* mod_sum(PyObject *self, PyObject *args)
{
    int a;
    int b;
    int s;
    if (!PyArg_ParseTuple(args,"ii",&a,&b))
       return NULL;
    s = sum(a,b);
    return Py_BuildValue("i",s);
}

static PyMethodDef ModMethods[] = {
    {"sum", mod_sum, METH_VARARGS, "Description.."},
    {NULL,NULL,0,NULL}
};

PyMODINIT_FUNC initmod(void)
{
    PyObject *m;
    m = Py_InitModule("module",ModMethods);
    if (m == NULL)
       return;
}

Python

import module
s = module.sum(3,5)

score 0 · Answer 2 · answered Apr 16 '13 at 03:42

Another option: try numba. It gives you C-like speed for free: just import numba and @autojit your functions, for a wonderful speed increase.

Won't work if you have complicated data types, but if you're looping and jumping around array indices, it might be just what you're looking for.

score 0 · Answer 3 · answered Apr 16 '13 at 03:43

0

you can use SWIG, it is very simple to use

answered Apr 16 '13 at 03:43

kaitian521

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score 0 · Answer 4 · answered May 08 '13 at 23:33

0

You can use Cython for setting the necessary c types and compile your python syntax code.

answered May 08 '13 at 23:33

tebanep

625
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Best way to call C-functions from python?

4 Answers4