#Personal Python Data Structure--PPDS##!/usr/bin/python# -*- coding: utf-8 -*-class Node(object):    def __init__(self,val,p=0):        self.data = val        self.next = p        self.prev = pclass LinkList(object):    def __init__(self):        self.head = 0    def initlist(self,data):        self.head = Node(data[0])        p = self.head        for i in data[1:]:            node = Node(i)            p.next = node            node.prev = p            p = p.next    def getlength(self):        length = 0        p =  self.head        while p != 0:            length+=1            p = p.next        return length    def is_empty(self):        if self.getlength() == 0:            return True        else:            return False    def clear(self):        self.head = 0    def append(self,item):        q = Node(item)        if self.head == 0:            self.head = q        else:            p = self.head            while p.next != 0:                p = p.next            p.next = q            q.prev = p    def getitem(self,index):        if self.is_empty():            print (‘Linklist is empty.‘)            return        j = 0        p = self.head        while p.next != 0 and j < index:            p = p.next            j+=1        if j == index:            return p.data        else:            print (‘target is not exist!‘)    def insert(self,index,item):        if self.is_empty() or index < 0 or index > self.getlength():            print (‘Linklist is empty.‘)            return        if index == 0:            q = Node(item,self.head)            self.head = q        j = 0                p = self.head        post  = self.head        while p.next != 0 and j < index:            post = p            p = p.next            j+=1        if index == j:            q = Node(item,p)            post.next = q            q.prev = post            q.next = p            p.prev = q    def delete(self,index):        if self.is_empty() or index < 0 or index > self.getlength():            print (‘Linklist is empty.‘)            return        if index ==0:            q = Node(item,self.head)            self.head = q        j = 0                p = self.head        post  = self.head        while p.next != 0 and j < index:            post = p            p = p.next            j+=1        if index ==j:            post.next = p.next            p.next.prev = post                def index(self,value):        if self.is_empty():            print (‘Linklist is empty.‘)            return        i = 0        p = self.head        while p.next != 0 and not p.data =http://www.mamicode.com/= value:            p = p.next            i+=1        if p.data =http://www.mamicode.com/= value:            return i        else:            return -1if __name__ == ‘__main__‘:    l=LinkList()    llist=[7,3,10,4,5,]    l.initlist(llist)    print(l.getlength())    print(l.is_empty())    # l.append(11)    # l.insert(2,100)    print(l.getlength())    print(l.getitem(0))    for i in range(l.getlength()):        print(l.index(llist[i]))    l.clear()    print(l.getlength())