I have put together a few c extensions following the documentation on
http://www.scipy.org/Cookbook/C_Extensions/NumPy_arrays. There is however
one thing that stumps me.
To illustrate with a simple code snippet, the test function below
multiplies the input numpy double array by two. So far so good. But how
about if I want the function to return a tuple of two numpy arrays so I
could do 'a, b = myCLib.test(c)' from a Python script? It's straight
forward to convert C data structures to Python objects with Py_BuildValue,
but how can I do this for numpy arrays instead?
static PyObject *
test(PyObject *self, PyObject *args)
{
PyArrayObject *py_in, *py_out;
double *in, *out;
int i, n, dims[2];
if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &py_in))
return NULL;
if (NULL == py_in || not_doublevector(py_in)) return NULL;
n = py_in->dimensions[0];
dims[0] = n;
dims[1] = 1;
py_out = (PyArrayObject *) PyArray_FromDims(1, dims, NPY_DOUBLE);
in = pyvector_to_Carrayptrs(py_in);
out = pyvector_to_Carrayptrs(py_out);
for (i=0; i<n; i++) {
out[i] = in[i] * 2.0;
}
return PyArray_Return(py_out);
}
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