#!/usr/bin/python # -*- coding: utf-8 -*- class TreeNode(object):     def __init__(self,data=0,left=0,right=0):         self.data = data         self.left = left         self.right = right class BTree(object):     def __init__(self,root=0):         self.root = root     def is_empty(self):         if self.root is 0:             return True         else:             return False     def preOrder(self,treenode):         if treenode is 0:             return         print treenode.data         self.preOrder(treenode.left)         self.preOrder(treenode.right)     def inOrder(self,treenode):         if treenode is 0:             return         self.inOrder(treenode.left)         print treenode.data         self.inOrder(treenode.right)     def postOrder(self,treenode):         if treenode is 0:             return         self.postOrder(treenode.left)         self.postOrder(treenode.right)         print treenode.data n1 = TreeNode(data=1) n2 = TreeNode(2,n1,0) n3 = TreeNode(3) n4 = TreeNode(4) n5 = TreeNode(5,n3,n4) n6 = TreeNode(6,n2,n5) n7 = TreeNode(7,n6,0) n8 = TreeNode(8) root = TreeNode('root',n7,n8) bt = BTree(root) print 'preOrder......' print bt.preOrder(bt.root) print 'inOrder......' print bt.inOrder(bt.root) print 'postOrder.....' print bt.postOrder(bt.root)