Python bidirectional linked lists implement instance code

Schematic diagram:
< img SRC = "border = 0 / / files.jb51.net/file_images/article/201311/20131121141652.jpg? 20131021142020 ">

Python two-way linked list implementation code :

#!/usr/bin/python
# -*- coding: utf-8 -*-
class Node(object):
    def __init__(self,val,p=0):
        self.data = val
        self.next = p
        self.prev = p
class LinkList(object):
    def __init__(self):
        self.head = 0
    def __getitem__(self, key):
        if self.is_empty():
            print 'linklist is empty.'
            return
        elif key <0  or key > self.getlength():
            print 'the given key is error'
            return
        else:
            return self.getitem(key)
 
    def __setitem__(self, key, value):
        if self.is_empty():
            print 'linklist is empty.'
            return
        elif key <0  or key > self.getlength():
            print 'the given key is error'
            return
        else:
            self.delete(key)
            return self.insert(key)
    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):
        p =  self.head
        length = 0
        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
        p = self.head
        post  = self.head
        j = 0
        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
        p = self.head
        post  = self.head
        j = 0
        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
        p = self.head
        i = 0
        while p.next!=0 and not p.data ==value:
            p = p.next
            i+=1
        if p.data == value:
            return i
        else:
            return -1

l = LinkList()
l.initlist([1,2,3,4,5])
print l.getitem(4)
l.append(6)
print l.getitem(5)
l.insert(4,40)
print l.getitem(3)
print l.getitem(4)
print l.getitem(5)
l.delete(5)
print l.getitem(5)
l.index(5)

The results for;

5
6
4
40
5
6

It's the same thing as a single linked list.