populate Python list passed as argument to C function

Question

I am writing a Python extension using C. How can I populate an empty list inside C when the list is passed as an argument and the C function does not return the list but a different PyObject*.

b=[]
a = c.populate(data=b)
print b

Output:

[1, 2, 3]

I appreciate your help. Thanks.

Answer 1

You can use the PyList_Append() function to add individual elements to an existing Python list object:

Append the object item at the end of list list. Return 0 if successful; return -1 and set an exception if unsuccessful. Analogous to list.append(item).

Alternatively, use PyList_SetSlice() to extend the list with items from another list object:

Set the slice of list between low and high to the contents of itemlist. Analogous to list[low:high] = itemlist. The itemlist may be NULL, indicating the assignment of an empty list (slice deletion). Return 0 on success, -1 on failure. Negative indices, as when slicing from Python, are not supported.