python 二叉排序樹

#! /usr/bin/env pythonclass BTNode:    def __init__(self, data, left, right):        self.data = data        self.left = left        self.right = rightclass BTree:    def __init__(self, root):        self.root = root;            def insert(self, value):        self.insertNode(value, self.root)            def insertNode(self, data, btnode):        if btnode == None:            btnode = BTNode(data, None, None)        elif data < btnode.data:            if btnode.left == None:                btnode.left = BTNode(data, None, None)                return                        self.insertNode(data,btnode.left)        elif data > btnode.data:            if btnode.right == None:                btnode.right = BTNode(data, None, None)                return                        self.insertNode(data,btnode.right)    def printBTreeImpl(self, btnode):        if btnode == None:            return            self.printBTreeImpl(btnode.left)        print btnode.data        self.printBTreeImpl(btnode.right)        def printBTree(self):        self.printBTreeImpl(self.root)    if __name__ == '__main__':        root = BTNode(2, None, None)    btree = BTree(root)    for i in [5, 8, 3, 1, 4, 9, 0, 7]:        btree.insert(i)        btree.printBTree()