Returning a tuple of tuples from c to python using ctypes - ctypes

Question

I need to return a two dimensional array of heterogenous data from my c dll to python.
I am returning a tuple of tuples for this purpose from my c dll. It is returned as PyObject *
This tuple of tuples needs to be accessed as tup[0][0] for the first row first column tup[0][1] for the first row second column ...and so on... in my python code.
I use ctypes to call the c function which returns the tuple of tuples. However , I am unable to access the returned PyObject* in the python code.
extern "C" _declspec(dllexport) PyObject *FunctionThatReturnsTuple()
{
PyObject *data = GetTupleOfTuples();
return data; //(PyObject*)pFPy_BuildValue("O", data);
}
In the python script I use the following -
libc = PyDLL("MyCDLL.dll")
x = libc.FunctionThatReturnsTuple()
if x != None :
print str( x[0][0] )
print str( x[0][1] )
However I get an error - 'int' object is not subscriptable. I think this is because x is received as pointer.
What is the right way to achieve this ?

Answer 1

You are not setting the return type of the "FunctionThatReturnsTuple".
In C:
#include <Python.h>
extern "C" PyObject* FunctionThatReturnsTuple()
{
PyObject* tupleOne = Py_BuildValue("(ii)",1,2);
PyObject* tupleTwo = Py_BuildValue("(ii)",3,4);
PyObject* data = Py_BuildValue("(OO)", tupleOne, tupleTwo);
return data;
}
Python:
>>> from ctypes import *
>>> libc = PyDLL("./test.dll")
>>> func = libc.FunctionThatReturnsTuple
>>> func()
-1215728020
>>> func.restype = py_object
>>> func()
((1, 2), (3, 4))