python求树的深度

def tree_depth(root):
    if root == None:
        return 0
    depth = 0
    temp = []
    temp.append(root)
    
    while len(temp):
        depth += 1
        length = len(temp)
        while length:
            pop = temp.pop()
            if pop.left != None:
                temp.append(pop.left)
            if pop.right != None:
                temp.append(pop.right)
            length -= 1
    return depth

队列先进先出,增加最后一个用append(),删除第一个用pop(0)
栈后进先出，出栈用pop()
不能用remove(), 因为不返回删除后的元素