#Though it looks like an ordinary python import, the addList module is implemented in C
import addList
l = [1,2,3,4,5]
print "Sum of List - " + str(l) + " = " + str(addList.add(l))
//Python.h has all the required function definitions to manipulate the Python objects
#include <Python.h>
//This is the function that is called from your python code
static PyObject* addList_add(PyObject* self, PyObject* args){
PyObject * listObj;
//The input arguments come as a tuple, we parse the args to get the various variables
//In this case it's only one list variable, which will now be referenced by listObj
if (! PyArg_ParseTuple( args, "O", &listObj ))
return NULL;
//length of the list
long length = PyList_Size(listObj);
//iterate over all the elements
int i, sum =0;
for (i = 0; i < length; i++) {
//get an element out of the list - the element is also a python objects
PyObject* temp = PyList_GetItem(listObj, i);
//we know that object represents an integer - so convert it into C long
long elem = PyInt_AsLong(temp);
sum += elem;
}
//value returned back to python code - another python object
//build value here converts the C long to a python integer
return Py_BuildValue("i", sum);
}
//This is the docstring that corresponds to our 'add' function.
static char addList_docs[] =
"add( ): add all elements of the list\n";
/* This table contains the relavent info mapping -
<function-name in python module>, <actual-function>,
<type-of-args the function expects>, <docstring associated with the function>
*/
static PyMethodDef addList_funcs[] = {
{"add", (PyCFunction)addList_add, METH_VARARGS, addList_docs},
{NULL, NULL, 0, NULL}
};
/*
addList is the module name, and this is the initialization block of the module.
<desired module name>, <the-info-table>, <module's-docstring>
*/
PyMODINIT_FUNC initaddList(void){
Py_InitModule3("addList", addList_funcs,
"Add all ze lists");
}
