Python program to delete a new node from the end of the doubly linked list

A doubly linked list is a data structure where each node contains three components: data, a pointer to the next node, and a pointer to the previous node. To delete a node from the end, we need to update the tail pointer and handle edge cases properly.

Node Class Structure

First, we create a Node class to represent individual elements in the doubly linked list ?

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

Doubly Linked List Implementation

The main class handles insertion, deletion, and display operations ?

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

class DoublyLinkedList:
    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.prev = None
            self.tail.next = None
        else:
            self.tail.next = new_node
            new_node.prev = self.tail
            self.tail = new_node
            self.tail.next = None

    def delete_from_end(self):
        if self.head == None:
            return
        else:
            if self.head != self.tail:
                self.tail = self.tail.prev
                self.tail.next = None
            else:
                self.head = self.tail = None

    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

# Create instance and test deletion
my_list = DoublyLinkedList()
print("Elements are being added to the doubly linked list")
my_list.add_data(10)
my_list.add_data(24)
my_list.add_data(54)
my_list.add_data(77)
my_list.add_data(92)
my_list.print_it()

# Delete elements from end one by one
while my_list.head != None:
    my_list.delete_from_end()
    print("The list after deleting the element from the end is:")
    my_list.print_it()

Elements are being added to the doubly linked list
The nodes in the doubly linked list are:
10
24
54
77
92
The list after deleting the element from the end is:
The nodes in the doubly linked list are:
10
24
54
77
The list after deleting the element from the end is:
The nodes in the doubly linked list are:
10
24
54
The list after deleting the element from the end is:
The nodes in the doubly linked list are:
10
24
The list after deleting the element from the end is:
The nodes in the doubly linked list are:
10
The list after deleting the element from the end is:
The list is empty

How the Delete Operation Works

The delete_from_end() method handles two main scenarios:

• Single node: When head equals tail, both are set to None
• Multiple nodes: The tail is moved to the previous node, and its next pointer is set to None

Key Points

• Always check if the list is empty before deletion
• Handle the case where only one node exists
• Update both prev and next pointers appropriately
• The tail pointer must be updated to maintain list integrity

Conclusion

Deleting from the end of a doubly linked list requires careful handling of the tail pointer and edge cases. The operation has O(1) time complexity since we maintain a direct reference to the tail node.