[capi-sig] Beginner Question PyObject* to int

[Chris Miles]

On 12/11/2008, at 1:55 AM, Philipp Heuser wrote:

> Hi all,
>
> I am just starting to use the C API for Python. What I want to do is  
> to use an external funtion availabele in C and therfore I want to  
> 'convert' a list of floats from Python to an array of floats in C  
> which I can forward to the external function. So first step is tp  
> parse a list to C and let the C code print the variables! The  
> obviously too simplistic approach is below... When I call this  
> function from python, e.g. cpp([1,2,3]) the output is:
> 25180552
> 25180540
> 25180528
>
> Could you be so kind to help me here to get started with using C- 
> functions from Python? Where is the error?
>
> Thank you very much and kind regards,
>
> Philipp
>
>
>
> static PyObject *
> cpp_foo(PyObject *self, PyObject* args)
> {
>      PyObject* obj;
>   PyObject* seq;
>      int i, len;
>      if(!PyArg_ParseTuple(args, "O", &obj))
>       return NULL;
>          seq = PySequence_Fast(obj, "expected a sequence");
>   len = PySequence_Size(obj);
>      PyObject* item;
>   int a;
>
>   for (i=0; i<len; i++)
>   {
>       item=PySequence_Fast_GET_ITEM(seq, i);
>       a=item;  // ?????????????????????????????????????????

Perhaps something like:

     long a;
     a = PyInt_AsLong(item);
     if (a == -1 && PyErr_Occurred())
         return NULL; /* error */
     printf("%i\n", a);

Cheers,
Chris Miles