Python program to create a doubly linked list of n nodes and display it in reverse order

When it is required to create a doubly linked list and display the elements in a reversed order, 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.

Another class needs to be created that would have an initialization function, and the head of the node would be initialized to ‘None’ inside this.

Multiple methods are defined by the user to add node to the linked list, to reverse the nodes and print the nodes in the linked list.

Below is a demonstration for the same −

Example

class Node:
   def __init__(self, my_data):
      self.prev = None
      self.data = my_data
      self.next = None
class reverse_list:
   def __init__(self):
      self.head = None
      self.tail = None
   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;
   def reverse_vals(self):
      curr = self.head;
      while(curr != None):
         temp = curr.next
         curr.next = curr.previous
         curr.previous = temp
         curr = curr.previous
      temp = self.head
      self.head = self.tail
      self.tail = temp
   def print_it(self):
      curr = self.head
      if (self.head == None):
         print("The list is empty")
         return
      print("The nodes are :")
      while curr != None:
         print(curr.data)
         curr = curr.next
my_instance = reverse_list()
print("Elements are being added to the list")
my_instance.add_data(10)
my_instance.add_data(14)
my_instance.add_data(24)
my_instance.add_data(17)
my_instance.add_data(22)
my_instance.print_it()
print("The reversed nodes in the doubly linked list are : ")
my_instance.reverse_vals()
my_instance.print_it()

Output

Elements are being added to the list
The nodes are :
10
14
24
17
22
The reversed nodes in the doubly linked list are :
The nodes are :
22
17
24
14
10

Explanation

• The ‘Node’ class is created.
• Another class with required attributes is created.
• A method named ‘add_data’ is defined, that is used to add data to the doubly linked list.
• Another method named ‘reverse_node’ is defined, that helps in reverse the order of nodes in the doubly linked list.
• Another method named ‘print_it’ is defined, that displays the nodes of the circular linked list.
• An object of the ‘reverse_list’ class is created, and the methods are called on it to reverse the nodes 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 ‘reverse_vals’ method is called.
• It iterates through the doubly linked list, and reverse the list.
• This is displayed on the console using the ‘print_it’ method.