doubly linked list head code example

Example 1: doubly linked list

# Initialise the Node
class Node:
    def __init__(self, data):
        self.item = data
        self.next = None
        self.prev = None
# Class for doubly Linked List
class doublyLinkedList:
    def __init__(self):
        self.start_node = None
    # Insert Element to Empty list
    def InsertToEmptyList(self, data):
        if self.start_node is None:
            new_node = Node(data)
            self.start_node = new_node
        else:
            print("The list is empty")
    # Insert element at the end
    def InsertToEnd(self, data):
        # Check if the list is empty
        if self.start_node is None:
            new_node = Node(data)
            self.start_node = new_node
            return
        n = self.start_node
        # Iterate till the next reaches NULL
        while n.next is not None:
            n = n.next
        new_node = Node(data)
        n.next = new_node
        new_node.prev = n
    # Delete the elements from the start
    def DeleteAtStart(self):
        if self.start_node is None:
            print("The Linked list is empty, no element to delete")
            return 
        if self.start_node.next is None:
            self.start_node = None
            return
        self.start_node = self.start_node.next
        self.start_prev = None;
    # Delete the elements from the end
    def delete_at_end(self):
        # Check if the List is empty
        if self.start_node is None:
            print("The Linked list is empty, no element to delete")
            return 
        if self.start_node.next is None:
            self.start_node = None
            return
        n = self.start_node
        while n.next is not None:
            n = n.next
        n.prev.next = None
    # Traversing and Displaying each element of the list
    def Display(self):
        if self.start_node is None:
            print("The list is empty")
            return
        else:
            n = self.start_node
            while n is not None:
                print("Element is: ", n.item)
                n = n.next
        print("\n")
# Create a new Doubly Linked List
NewDoublyLinkedList = doublyLinkedList()
# Insert the element to empty list
NewDoublyLinkedList.InsertToEmptyList(10)
# Insert the element at the end
NewDoublyLinkedList.InsertToEnd(20)
NewDoublyLinkedList.InsertToEnd(30)
NewDoublyLinkedList.InsertToEnd(40)
NewDoublyLinkedList.InsertToEnd(50)
NewDoublyLinkedList.InsertToEnd(60)
# Display Data
NewDoublyLinkedList.Display()
# Delete elements from start
NewDoublyLinkedList.DeleteAtStart()
# Delete elements from end
NewDoublyLinkedList.DeleteAtStart()
# Display Data
NewDoublyLinkedList.Display()

Example 2: doubly linked list example

//insert link at the first location
void insertFirst(int key, int data) {

   //create a link
   struct node *link = (struct node*) malloc(sizeof(struct node));
   link->key = key;
   link->data = data;
	
   if(isEmpty()) {
      //make it the last link
      last = link;
   } else {
      //update first prev link
      head->prev = link;
   }

   //point it to old first link
   link->next = head;
	
   //point first to new first link
   head = link;
}