[Numpy-discussion] Complete and build the example from the "Using Numpy C-API" documentation.

Warren Weckesser warren.weckesser@enthought....
Tue Jul 20 18:04:42 CDT 2010

Warren Weckesser wrote:
> I would like to take the example shown here:
>   http://docs.scipy.org/doc/numpy/user/c-info.how-to-extend.html#example
> and complete the code so I can build and test the extension module.  Is 
> that example currently correct?  It is slightly different from the older 
> example in the numpy book, so someone must have had a reason to change it. 
> I've added the C array of PyMethodDefs and the module init function, but 
> I'm still searching for the correct #includes for the numpy stuff.  Any 
> suggestions (or pointers to similar simple but complete examples) would 
> be appreciated.

I've made some progress, and now I'm getting a bus error.
With the following extension module, calling example.foo results
in a bus error, regardless of the arguments given.  The error
occurs in the call to PyArg_ParseTuple.  I'm using same format
string as in the example in the numpy docs, "O!".  Any ideas?

#include <stdio.h>
#include "Python.h"
#include "numpy/arrayobject.h"

static PyObject *foo_wrap(PyObject *dummy, PyObject *args)
    PyObject *arg1 = NULL;

    if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &arg1)) {
        return NULL;
    return Py_None;

static PyMethodDef wrappers[] = {
    {"foo", foo_wrap, METH_VARARGS, "just a test"},
    {NULL, NULL, 0, NULL}        /* Sentinel */

    (void) Py_InitModule("example", wrappers);
> Warren
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