I am writing C extensions for python.
I want to know how to add a C object to python list using PyList_SetItem.
For example,
I have a C object.
Atom *a = (Atom *)(PyTuple_GET_ITEM(tmp2, 0));
I made a list:
PyObject* MyList = PyList_New(3);
I am not sure what the third argument must be in the following statement.
PyObject_SetItem(MyList, 0, a);
Also how do I return this list of C objects to python.
The third argument to PyList_SetItem is the Python Object to be added to the list, which is usually converted from a C type, as in this simple example:
/* This adds one to each item in a list. For example:
alist = [1,2,3,4,5]
RefArgs.MyFunc(alist)
*/
static PyObject * MyFunc(PyObject *self, PyObject *args)
{
PyObject * ArgList;
int i;
PyArg_ParseTuple(args, "O!", &PyList_Type, &ArgList));
for (i = 0; i < PyList_Size(ArgList); i++)
{
PyObject * PyValue;
long iValue;
PyValue = PyList_GetItem(ArgList, i);
/* Add 1 to each item in the list (trivial, I know) */
iValue = PyLong_AsLong(PyValue) + 1;
/* SETTING THE ITEM */
iRetn = PyList_SetItem(ArgList, i, PyLong_FromLong(iValue));
if (iRetn == -1) Py_RETURN_FALSE;
}
Py_RETURN_TRUE;
}
PyObject_SetItem is similar. The difference is that PyList_SetItem steals the reference, but PyObject_SetItem only borrows it. PyObject_SetItem cannot be used with an immutable object, like a tuple.
PyList_SetItem does. The OP specifically asked for this API, but of course it does not append: PyList_Append() is required for that (or PyList_Insert() could be used).