[capi-sig] How to manipulate C table as python list ?

[Stefan Behnel]

Hrvoje Niksic wrote:
> PyObject *sum(PyObject *ignored, PyObject *lst)
> {
>     int i, s = 0;
>     if (!PyList_Check(lst)) {
>         PyErr_Format(PyExc_TypeError, "sum: expected list, got %s",
>                      lst->ob_type->tp_name);
>         return NULL;
>     }
>     for (i = 0; i < PyList_GET_SIZE(lst); i++) {
>         ... sum the list ...
>     return PyInt_FromLong(s);
> }
> 
>> My question is:
>> which option should I use with PyArg_ParseTuple?
> 
> If your function is declared to take one argument with METH_O, you
> don't need PyArg_ParseTuple at all.  If it's declared to take a
> variable number of arguments, you'd use it like this:
> 
> PyObject *sum(PyObject *ignored, PyObject *args)
> {
>     int i, s = 0;
>     PyObject *lst;
>     if (!PyArg_ParseTuple(args, "O", &lst))
>         return NULL;
>     ...
> }

You can also write your code in Cython. The following Cython code will
generate roughly the same C code that you present above:

    def sum(list l):
        cdef int i, s = 0
        for i in l:
            s += i
        return s

http://cython.org/

Stefan