Python single linked list implementation code instance

Definition of linked list:
A linked list is a data structure consisting of a set of data elements called nodes, each of which contains information about the node itself and the address to the next node. Since each node contains address information that can be linked together, the entire sequence of nodes can be accessed with a single variable. In other words, nodes contain two parts of information: one part is used to store the value of data elements, called information field; The other part stores a pointer to the address of the next data element, called a pointer field. The address of the first node in a linked list is stored in a separate node, called the head or first node. The last node in the list has no successor and its pointer field is empty.

Python single 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
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
            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

    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.next = p

    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
    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)

Results:

5
6
4
40
5
6