wrapping C functions in python

[Brian Cole]

We use the following SWIG (www.swig.org) typemap to perform such operations:

%typemap(in) (int argc, char **argv) {
  if (!PySequence_Check($input)) {
    PyErr_SetString(PyExc_ValueError,"Expected a sequence");
    return NULL;
  }
  $1 = PySequence_Length($input);
  $2 = (char**)alloca($1*sizeof(char*));
  for (Py_ssize_t i = 0; i < $1; ++i) {
    PyObject *o = PySequence_GetItem($input, i);
    $2[i] = PyString_AsString(o);
  }
}

That one works for mapping a python sequence (such as a list) into the
argc, argv arguments commonly passed into main.

-Brian

On Wed, Apr 9, 2008 at 2:13 PM, Paul Anton Letnes
<paul.anton.letnes at gmail.com> wrote:
> Hello etc.
>
>
> I am a "scientific" user of Python, and hence have to write some performance
> critical algorithms. Right now, I am learning Python, so this is a "newbie"
> question.
>
> I would like to wrap some heavy C functions inside Python, specifically a
> wavelet transform. I am beginning to become aquainted with the functions
> PyArg_ParseTuple() and Py_BuildValue(). However, I am unable to figure out
> how to pass Python list -> C function or C array -> return value in Python.
> I manage to build and run the C function, print to screen, pass string as
> argument, return an int, etc. The thing which is missing is the magic
> array/list...
>
>
> Thanks in advance! I fart in your general direction.
> Paul.
> --
>  http://mail.python.org/mailman/listinfo/python-list
>