Delete from Beginning of Doubly Linked List in DSA Python - Build from Scratch

Delete from Beginning of Doubly Linked List

📖 Scenario: You are managing a playlist of songs where each song is linked to the previous and next song. Sometimes, you want to remove the first song from the playlist.

🎯 Goal: Build a doubly linked list with three songs, then delete the first song from the list, and finally print the updated playlist.

📋 What You'll Learn

Create a doubly linked list with three nodes containing the exact song names: 'Song1', 'Song2', 'Song3'.

Create a variable called head pointing to the first node.

Write a function called delete_from_beginning that removes the first node from the doubly linked list.

Print the updated list starting from head after deletion.

💡 Why This Matters

🌍 Real World

Doubly linked lists are used in music players, web browsers (back and forward navigation), and undo-redo features where you need to move both forward and backward.

💼 Career

Understanding how to manipulate doubly linked lists is important for software engineers working on systems that require efficient insertions and deletions from both ends, such as caches and navigation history.

1

Create the Doubly Linked List with Three Songs

Create a class called Node with attributes data, prev, and next. Then create three nodes with data 'Song1', 'Song2', and 'Song3'. Link them to form a doubly linked list and set head to the first node.

DSA Python

# Define Node class and create three linked nodes
# Your code here

Hint

Remember to link nodes both ways: next and prev.

2

Create a Function to Delete from Beginning

Create a function called delete_from_beginning that takes head as input and returns the new head after deleting the first node. If the list is empty, return None. If there is a next node, update its prev to None.

DSA Python

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

node1 = Node('Song1')
node2 = Node('Song2')
node3 = Node('Song3')

node1.next = node2
node2.prev = node1
node2.next = node3
node3.prev = node2

head = node1

# Define delete_from_beginning function below
# Your code here

Hint

Check if head is None first. Then update new_head.prev to None if it exists.

3

Delete the First Node from the List

Call the function delete_from_beginning with the variable head and update head with the returned new head.

DSA Python

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

node1 = Node('Song1')
node2 = Node('Song2')
node3 = Node('Song3')

node1.next = node2
node2.prev = node1
node2.next = node3
node3.prev = node2

head = node1

def delete_from_beginning(head):
    if head is None:
        return None
    new_head = head.next
    if new_head is not None:
        new_head.prev = None
    return new_head

# Call delete_from_beginning and update head
# Your code here

Hint

Assign the result of delete_from_beginning(head) back to head.

4

Print the Updated Doubly Linked List

Use a while loop with a variable current starting at head to print the data of each node separated by -> . End the print with null.

DSA Python

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

node1 = Node('Song1')
node2 = Node('Song2')
node3 = Node('Song3')

node1.next = node2
node2.prev = node1
node2.next = node3
node3.prev = node2

head = node1

def delete_from_beginning(head):
    if head is None:
        return None
    new_head = head.next
    if new_head is not None:
        new_head.prev = None
    return new_head

head = delete_from_beginning(head)

# Print the doubly linked list starting from head
# Your code here

Hint

Use a loop to print each node's data followed by -> , then print null at the end.