Help me understand Inorder Traversal without using recursion

Question

I am able to understand preorder traversal without using recursion, but I\'m having a hard time with inorder traversal. I just don\'t seem to get it, perhaps, because I have

Answer 1

def print_tree_in(root):
    stack = []
    current = root
    while True:
        while current is not None:
            stack.append(current)
            current = current.getLeft();
        if not stack:
            return
        current = stack.pop()
        print current.getValue()
        while current.getRight is None and stack:
            current = stack.pop()
            print current.getValue()
        current = current.getRight();