how to programming pre / in order traversal without recursion in python

Question

here is my code about postorder_nonrecursive. I want to know preorder and inorder like this code. please help me!

def postorder_nonrecursive(self):
        if self == None:
            return
        stack = [[self,0]] 

        while len(stack) > 0:
            node, state = stack[-1]

            if state == 2:
                yield node
                stack.pop()
            else:
                child = (node.getLeft() if state == 0 else node.getRight())
                stack[-1][1] += 1

                if child != None:
                    stack.append([child,0])