PyListObject & C Modules

[Martin v. Loewis]

Brian Quinlan <brian at sweetapp.com> writes:

>   if(PyList_Size(list) == 0){
>     PyErr_SetString(PyExc_ValueError, "empty lists not allowed");
>     return NULL;
>   }
>  
>   first = PyList_GetItem(list, 0);
> + if (first == NULL) return NULL;

That can't happen, really - GetItem can fail only if it is not a list,
or if the index is out of range. However, it is a good strategy to
test all results.

> + Py_ADDREF(first)
> - PyList_SetItem(result, 0, first);
> + if (PyList_SetItem(result, 0, first) != 0) {
> +   Py_DECREF(first)
> +   Py_DECREF(result);
> +   result = NULL;
> + }

I see: yes, this is needed. I wasn't really aware that SetItem steals
a reference. This is counter-intuitive - it might be better to use
PySequence_SetItem instead.

Regards,
Martin