On the Python side, I can create new numpy record arrays as follows:
numpy.zeros((3,), dtype=[('a', 'i4'), ('b', 'U5')])
How do I do the same from a C program? I suppose I have to call PyArray_SimpleNewFromDescr(nd, dims, descr), but how do I construct a PyArray_Descr that is appropriate for passing as the third argument to PyArray_SimpleNewFromDescr?
Use PyArray_DescrConverter. Here's an example:
#include <Python.h>
#include <stdio.h>
#include <numpy/arrayobject.h>
int main(int argc, char *argv[])
{
int dims[] = { 2, 3 };
PyObject *op, *array;
PyArray_Descr *descr;
Py_Initialize();
import_array();
op = Py_BuildValue("[(s, s), (s, s)]", "a", "i4", "b", "U5");
PyArray_DescrConverter(op, &descr);
Py_DECREF(op);
array = PyArray_SimpleNewFromDescr(2, dims, descr);
PyObject_Print(array, stdout, 0);
printf("\n");
Py_DECREF(array);
return 0;
}
Thanks to Adam Rosenfield for pointing to Section 13.3.10 of the Guide to NumPy.
See the Guide to NumPy, section 13.3.10. There's lots of different ways to make a descriptor, although it's not nearly as easy as writing [('a', 'i4'), ('b', 'U5')].
PyArray_DescrConverter, which works. I've posted an example as a separate answer, as it doesn't fit in a comment.
