python-树形结构和遍历

 #!/usr/bin/python

 class TreeNode(object):
     def __init__(self,data = 0,left = None,right = None):
         self.data = data
         self.left = left
         self.right = right

 class Bitree(object):
     def __init__(self,root=None):
         self.root = root

     def is_empty(self):
         if self.root is None:
             return True
         else:
             return False

     def preOrder(self,treenode):
         if treenode is None:
             return

         print(treenode.data)
         self.preOrder(treenode.left)
         self.preOrder(treenode.right)

     def inOrder(self,treenode):

         if treenode is None:
             return

         self.inOrder(treenode.left)
         print(treenode.data)
         self.inOrder(treenode.right)

     def postOrder(self,treenode):

         if treenode is None:
             return

         self.postOrder(treenode.left)
         self.postOrder(treenode.right)
         print(treenode.data)

 n1 = TreeNode(1)
 n2 = TreeNode(2,n1)
 n3 = TreeNode(3)
 n4 = TreeNode(4)
 n5 = TreeNode(5,n3,n4)
 n6 = TreeNode(6,n2,n5)
 n7 = TreeNode(7,n6)
 n8 = TreeNode(8)
 root = TreeNode('root',n7,n8)

 bt = Bitree(root)
 print ('preOrder......')
 print (bt.preOrder(bt.root))
 print ('inOrder......')
 print (bt.inOrder(bt.root))
 print ('postOrder.....')
 print (bt.postOrder(bt.root))