python 双向链表

#coding:utf-8class DoubleLinked:    def __init__(self):        self.DL = self.Node(None) # 哨兵    def insert(self, k):        self.pprint()        node = self.Node(k)        p = self.DL        temp = p.next        while temp and cmp(temp.k, k) == 1:            p = temp            temp = temp.next        node.pre = p        node.next = temp        p.next = node        if temp:            temp.pre = node    def search(self, k):        node = self.DL.next        while node and cmp(node.k, k) != 0:            node = node.next        return node    def remove(self,k):        self.pprint()        node = self.search(k)        if node:            node.pre.next = node.next            if node.next:                node.next.pre = node.pre            print 'delete %s ' % str(k)        else:            print 'not find %s ' % str(k)    def pprint(self):        node = self.DL        while node:            print '%s(%s %s %s)' % (str(id(node)), node.pre, str(node.k), node.next),            node = node.next        print    @classmethod    def test(cls):        DL = cls()        DL.insert(20)        DL.insert(18)        DL.insert(21)        DL.insert(19)        DL.remove(24)        DL.remove(21)        DL.remove(19)        DL.remove(18)        DL.remove(24)        DL.remove(20)        DL.remove(20)        DL.pprint()        print 'test over'    class Node:        def __init__(self, k):            self.pre = self.next = None            self.k = k        def __str__(self):            return str(id(self))DoubleLinked.test()