One can learn the basics of Linked List from the following video tutorial:

Here’s a program which implements Singly Linked Lists in python:

The first and the foremost thing is that we must represent a node of a list. Here’s a representation of a node:

#class for defining a Node in a list class Node(object): def __init__(self,value,nextNode=None): self.value = value self.next = nextNode

The value field consists the value assigned to the node, and the next field consists the reference to the next node.

After this we need to create the Linked List class which actually holds the nodes and operates on them. The following class represents Linked Lists and the its basic operations:

#class for defining a linked list class LinkedList(object): #initializing a list def __init__(self): self.length = 0 self.head = None #method to add a node in the linked list def addNode(self,node): if self.length == 0: self.addBeg(node) else: self.addLast(node) #method to add a node at the beginning of the list with a value def addBeg(self,node): newNode = node newNode.next = self.head self.head = newNode self.length += 1 #method to add a node after the node having the value=value1. The value of the new node is value2 def addAfterValue(self,value1,node): newNode = node currentnode = self.head while currentnode.next != None or currentnode.value != value1: if currentnode.value == value1: newNode.next = currentnode.next currentnode.next = newNode self.length = self.length + 1 return else: currentnode = currentnode.next print "The value provided is not present" #method to add a node at a particular position def addAtPos(self,pos,node): count = 0 currentnode = self.head previousnode = self.head if pos > self.length or pos < 0: print "The position does not exist. Please enter a valid position" else: while currentnode.next != None or count < pos: count = count + 1 if count == pos: previousnode.next = node node.next = currentnode self.length += 1 return else: previousnode = currentnode currentnode = currentnode.next #method to add a node at the end of a list def addLast(self,node): currentnode = self.head while currentnode.next != None: currentnode = currentnode.next newNode = node newNode.next = None currentnode.next = newNode self.length = self.length + 1 #method to delete the first node of the linked list def deleteBeg(self): if self.length == 0: print "The list is empty" else: self.head = self.head.next self.length -= 1 #method to delete the last node of the linked list def deleteLast(self): if self.length == 0: print "The list is empty" else: currentnode = self.head previousnode = self.head while currentnode.next != None: previousnode = currentnode currentnode = currentnode.next previousnode.next = None self.length -= 1 #method to delete a node after the node having the given value def deleteValue(self,value): currentnode = self.head previousnode = self.head while currentnode.next != None or currentnode.value != value: if currentnode.value == value: previousnode.next = currentnode.next self.length -= 1 return else: previousnode = currentnode currentnode = currentnode.next print "The value provided is not present" #method to delete a node at a particular position def deleteAtPos(self,pos): count = 0 currentnode = self.head previousnode = self.head if pos > self.length or pos < 0: print "The position does not exist. Please enter a valid position" else: while currentnode.next != None or count < pos: count = count + 1 if count == pos: previousnode.next = currentnode.next self.length -= 1 return else: previousnode = currentnode currentnode = currentnode.next #returns the length of the list def getLength(self): return self.length #returns the first element of the list def getFirst(self): if self.length == 0: print "The list is empty" else: return self.head.value #returns the last element of the list def getLast(self): if self.length == 0: print "The list is empty" else: currentnode = self.head while currentnode.next != None: currentnode = currentnode.next return currentnode.value #returns node at any position def getAtPos(self,pos): count = 0 currentnode = self.head if pos > self.length or pos < 0: print "The position does not exist. Please enter a valid position" else: while currentnode.next != None or count < pos: count = count + 1 if count == pos: return currentnode.value else: currentnode = currentnode.next #method to print the whole list def print_list(self): nodeList = [] currentnode = self.head while currentnode!= None: nodeList.append(currentnode.value) currentnode = currentnode.next print nodeList node1 = Node(1) node2 = Node(2) node3 = Node(3) node4 = Node(4) ll = LinkedList() ll.addNode(node1) ll.addNode(node2) ll.addNode(node3) ll.addNode(node4) ll.print_list() #output = [1, 2, 3, 4] node5 = Node(5) ll.addAtPos(3,node5) ll.print_list() #Output = [1, 2, 5, 3, 4] ll.deleteAtPos(2) ll.print_list() #Output = [1, 5, 3, 4]