Insert New Node at the Middle of Doubly Linked List in Python

When it is required to insert a new node in the middle 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.previous = None
      self.data = my_data
      self.next = None
class double_list:
   def __init__(self):
      self.head = None
      self.tail = None
      self.size = 0
   def add_data(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.next = new_node
         new_node.previous = self.tail
         self.tail = new_node
         self.tail.next = None
      self.size = self.size + 1
   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
   def add_data_in_middle(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:
         curr = self.head;
         mid = (self.size//2) if(self.size % 2 == 0) else ((self.size+1)//2);
         for i in range(1, mid):
            curr = curr.next;
         temp = curr.next;
         temp.previous = curr;
         curr.next = new_node;
         new_node.previous = curr;
         new_node.next = temp;
         temp.previous = new_node;
      self.size = self.size + 1;
my_instance = double_list()
print("Elements are being added to the doubly linked list")
my_instance.add_data(10)
my_instance.add_data(24)
my_instance.add_data(54)
print("Elements are added to the middle of the list")
my_instance.add_data_in_middle(77)
my_instance.print_it()
my_instance.add_data_in_middle(92)
my_instance.print_it()

Output

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

Explanation

• The ‘Node’ class is created.
• Another class with required attributes is created.
• A method named ‘add_data_in_middle’ is defined, that is used to add data in the middle index of the doubly linked list.
• A method named ‘add_data’ is defined, that helps add nodes to 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 doubly linked list.
• The ‘add_data_in_middle’ is called to add data to middle index of the linked list.
• An ‘init’ method is defined, that the root, head, and tail nodes of the doubly linked list to None.
• This is displayed on the console using the ‘print_it’ method.