直观打印二叉树 Python

class Node(object):
    def __init__(self,val=None):
        self.val = val
        self.left = None
        self.right = None
 

def printTree(root):
    if not root:
        return
    print('Binary Tree')
    printInorder(root, 0, 'H', 17)
def printInorder(root, height, preStr, length):
    if not root:
        return 
    printInorder(root.right, height+1, 'V', length)
    string = preStr + str(root.val) + preStr
    leftLen = (length - len(string))//2
    rightLen = length - len(string) - leftLen
    res = " "*leftLen + string + " "*rightLen
    print(" "*height*length + res)
    printInorder(root.left, height+1, '^',length)

 
head = Node(1)
head.left = Node(-222222222)
head.right = Node(3)
head.left.left = Node(523)
head.right.left = Node(55555555)
head.right.right =  Node(66)
head.left.left.right = Node(777)
printTree(head)