dll python

# program to implement Doubly Linked List
class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None

    # returns true is DoublyLinkedList is Empty
    def isEmpty(self):
        if self.head is None:
            return True
        else:
            return False

    # method adds elements to the left of the Linked List
    def addToStart(self, data):
        # create a temporary node
        tempNode = Node(data)
        if self.head is not None:
            tempNode.setNextLink(self.head)
            self.head.setPrevLink(tempNode)
            self.head = tempNode
        elif self.head is None:
            self.head = tempNode
            self.tail = tempNode

        del tempNode

    # method adds elements to the right of the Linked List
    def addToEnd(self, data):
        end = self.tail
        tempNode = Node(data)
        end.setNextLink(tempNode)
        tempNode.setPrevLink(end)
        self.tail = tempNode
        del tempNode
        return True

    # method displays Linked List
    def display(self):
        start = self.head
        if start is None:
            print("Empty List!!!")
            return False

        while start:
            print(str(start.getData()), end=" ")
            start = start.getNextNode()
            if start:
                print("<-->", end=" ")
        print()


# node class
class Node:
    # default value of data and prevlink and nextLink is none if no data is passed
    def __init__(self, data=None, prevlink=None, nextLink=None):
        self.data = data
        self.prevlink = prevlink
        self.nextLink = nextLink

    # method to update the data feild of Node
    def updateData(self, data):
        self.data = data

    # method to set prevlink feild the Node
    def setPrevLink(self, node=None):
        self.prevlink = node

    # method to set nextlink feild the Node
    def setNextLink(self, node=None):
        self.nextLink = node

    # method returns data feild of the Node
    def getData(self):
        return self.data

    # method returns address of the next Node
    def getNextNode(self):
        return self.nextLink

    # method returns address of the next Node
    def getPreviousNode(self):
        return self.prevlink


# main method
# creating DoublyLinkedList
myList = DoublyLinkedList()

# adding some elements to the start of LinkedList
myList.addToStart(5)
myList.addToStart(4)
myList.addToStart(3)
myList.addToStart(2)
myList.addToStart(1)


myList.display()

# adding some elements to the End of the DoublyLinkedList
myList.addToEnd(12)
myList.addToEnd(13)
myList.addToEnd(3)
myList.display()