python先序遍历二叉树问题

# !/usr/bin/env python/197725.html">python# -*-encoding: utf-8-*-# author:LiYanwei# version:0.1class TreeNode(object):  '''  二叉树类  '''  def __init__ (self, data, left = None, right = None):    self.data = data    self.left = left    self.right = right  def __str__(self):    return str(self.data)def createTree():  '''  创建二叉树函数  '''  # 创建如图的二叉树  # 1.创建节点  A = TreeNode('A')  B = TreeNode('B')  C = TreeNode('C')  D = TreeNode('D')  E = TreeNode('E')  F = TreeNode('F')  # 列表解析  # A, B, C, D, E, F = [TreeNode(x) for x in 'ABCDEF']  # 2.创建节点之间的关系  A.left = B  A.right = C  B.left = D  B.right = E  C.left = F  return Adef preOrder(node):  '''  先序遍历 先左后右 使用递归  :param node:  :return:  '''  if node is None:    return  print node.data  preOrder(node.left)  preOrder(node.right)if __name__ == '__main__':  # 二叉树的创建  root = createTree()  # 二叉树的遍历  preOrder(root)