Stack sort in python(using system stack)

gistfile1.py

def stackInsert(stack, elem):
    if len(stack) == 0 or stack[len(stack)-1] <= elem:
        stack.append(elem)
    else:
        topElem = stack.pop()
        stackInsert(stack, elem)
        stack.append(topElem)

def stackSort(stack):
    if len(stack) == 0:
        return
    elem = stack.pop()
    stackSort(stack)
    stackInsert(stack, elem)