二叉树 前中后序遍历

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

class BinaryTree:
    def __init__(self):
        pass
    
def preTraverse(root):
    """
    前序遍历
    """
    if root == None:
        return
    print(root.data)
    preTraverse(root.left)
    preTraverse(root.right)

def midTraverse(root):
    """
    中序遍历
    """
    if root == None:
        return
    midTraverse(root.left)
    print(root.data)
    midTraverse(root.right)

def afterTraverse(root):
    """
    后序遍历
    """
    if root == None:
        return
    afterTraverse(root.left)
    afterTraverse(root.right)
    print(root.data)