python先序遍历二叉树问题

# !/usr/bin/env python
# -*-encoding: utf-8-*-
# author:LiYanwei
# version:0.1


class 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 A


def 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)