doubly linked list.py

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
        self.prev = None


class DoublyLinkedList:
    def __init__(self):
        self.head = None

    def printList(self):
        temp = self.head
        while temp:
            print(temp.data)
            temp = temp.next

    def append(self, data):
        if not self.head:
            new_node = Node(data)
            new_node.prev = None
            self.head = new_node
        else:
            new_node = Node(data)
            temp = self.head
            while temp.next:
                temp = temp.next
            temp.next = new_node
            new_node.prev = temp
            new_node.next = None

    def prepend(self, data):
        if not self.head:
            new_node = Node(data)
            new_node.prev = None
            self.head = new_node
        else:
            new_node = Node(data)
            self.head.prev = new_node
            new_node.next = self.head
            self.head = new_node
            new_node.prev = None


if __name__ == '__main__':

    dlist = DoublyLinkedList()
    dlist.append(10)
    dlist.append(20)
    dlist.prepend(30)
    dlist.printList()