Insert New Node at the Beginning of a Doubly Linked List in Python

When it is required to insert a new node at the beginning of a doubly linked list, a ‘Node’ class needs to be created. In this class, there are three attributes, the data that is present in the node, the access to the next node of the linked list, and the access to the previous node of the linked list.

Below is a demonstration for the same −

Example

 Live Demo

class Node:
   def __init__(self, my_data):
      self.prev = None
      self.data = my_data
      self.next = None
class double_list:
   def __init__(self):
      self.head = None
      self.tail = None
   def add_data_at_start(self, my_data):
      new_node = Node(my_data)
      if(self.head == None):
         self.head = self.tail = new_node
         self.head.previous = None
         self.tail.next = None
      else:
         self.tail.previous = new_node
         new_node.next = self.head
         new_node.previous = None
         self.head = new_node
   def print_it(self):
      curr = self.head
      if (self.head == None):
         print("The list is empty")
         return
      print("The nodes in the doubly linked list are :")
      while curr != None:
         print(curr.data)
         curr = curr.next
my_instance = double_list()
print("Elements are being added to the beginning of doubly linked list")
my_instance.add_data_at_start(10)
my_instance.print_it()
my_instance.add_data_at_start(24)
my_instance.print_it()
my_instance.add_data_at_start(54)
my_instance.print_it()
my_instance.add_data_at_start(77)
my_instance.print_it()
my_instance.add_data_at_start(92)
my_instance.print_it()

Output

Elements are being added to the beginning of doubly linked list
The nodes in the doubly linked list are :
10
The nodes in the doubly linked list are :
24
10
The nodes in the doubly linked list are :
54
24
10
The nodes in the doubly linked list are :
77
54
24
10
The nodes in the doubly linked list are :
92
77
54
24
10

Explanation

• The ‘Node’ class is created.
• Another class with required attributes is created.
• A method named ‘add_data_at_start’ is defined, that is used to add data at the beginning of the doubly linked list.
• Another method named ‘print_it’ is defined, that displays the nodes of the circular linked list.
• An object of the ‘double_list’ class is created, and the methods are called on it to add data to the beginning of the doubly linked list.
• An ‘init’ method is defined, that the root, head, and tail nodes of the doubly linked list to None.
• The list is iterated over, and the element is added to the beginning of the doubly linked list.
• This is displayed on the console using the ‘print_it’ method.