levelorder.py

def levelorder(root: TreeNode) -> None:
    if not root: return
    q = deque([root])
    
    while q:
        size = len(q)
        for i in range(size):
            node = q.popleft()
            print(str(node.val), end = " ")
            if node.left: 
                q.append(node.left)
            if node.right: 
                q.append(node.right)

        print()