python 二叉树

#coding:utf-8
__author__ = 'similarface'

class BinaryTree:
    def __init__(self):
        self.tree=EmptyNode()
    def __repr__(self):
        return repr(self.tree)
    def lookup(self, value):
        return self.tree.lookup(value)
    def insert(self, value):
        self.tree = self.tree.insert(value)

class EmptyNode:
    def __repr__(self):
        return '*'
    #叶子节点返回false
    def lookup(self,value):
        return False
    #树的低端添加新节点
    def insert(self,value):
        return BinaryNode(self,value,self)

class BinaryNode:
    def __init__(self,left,value,right):
        print(left,value,right)
        self.data, self.left, self.right = value,left,right

    def lookup(self,value):
        if self.data==value:
            return True
        elif self.data>value:
            return self.left.lookup(value)
        else:
            return self.right.lookup(value)
    def insert(self,value):
        if self.data>value:
            self.left=self.left.insert(value)
        elif self.data<value:
            self.right=self.right.insert(value)
        return self

    def __repr__(self):
        return ('( %s, %s, %s )' % (repr(self.left), repr(self.data), repr(self.right)))

if __name__=="__main__":
    x=BinaryTree()
    for i in [3,1,2]:
        x.insert(i)

    for i in range(8):
        print((i,x.lookup(i)))
    print('---------------------')
    y=BinaryTree()
    for i in [3,1,9,2,7]:
        y.insert(i)
        print(y)
    print('----------z-----------')
    z=BinaryTree()
    for c in 'badce':
        z.insert(c)
    print(z)