Creating a Singly Linked List from Scratch in DSA Python - Code It Step by Step

Creating a Singly Linked List from Scratch

📖 Scenario: Imagine you want to keep a list of your favorite fruits in order. You want to add fruits one by one and see the list grow. A singly linked list is like a chain where each fruit points to the next fruit in the list.

🎯 Goal: You will build a simple singly linked list from scratch in Python. You will create nodes, link them together, and finally print the list to see all fruits in order.

📋 What You'll Learn

Create a Node class with two attributes: data and next

Create a LinkedList class with a head attribute initialized to None

Add a method append to add new nodes to the end of the list

Add a method print_list to display all nodes in the list in order

💡 Why This Matters

🌍 Real World

Singly linked lists are used in many places like music playlists, undo history in apps, and managing tasks in order.

💼 Career

Understanding linked lists helps in coding interviews and building efficient data structures for software development.

1

Create the Node class

Create a class called Node with an __init__ method that takes data as a parameter and sets self.data = data and self.next = None.

DSA Python

# Your code here

Hint

Think of each node as a box holding a fruit name and a pointer to the next box.

2

Create the LinkedList class with head

Create a class called LinkedList with an __init__ method that sets self.head = None.

DSA Python

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

# Your code here

Hint

The linked list starts empty, so the head points to nothing.

3

Add append method to LinkedList

Inside the LinkedList class, add a method called append that takes data as a parameter. Create a new Node with this data. If self.head is None, set self.head to the new node. Otherwise, traverse the list to the last node and set its next to the new node.

DSA Python

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

class LinkedList:
    def __init__(self):
        self.head = None

    # Your code here

Hint

Think of walking down the chain until you find the last box, then attach the new box there.

4

Add print_list method and print the list

Inside the LinkedList class, add a method called print_list that starts from self.head and prints each node's data followed by -> until the end of the list, then prints None. After the class definitions, create a LinkedList object called fruits, append 'Apple', 'Banana', and 'Cherry' to it, then call fruits.print_list().

DSA Python

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

class LinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
            return
        last = self.head
        while last.next:
            last = last.next
        last.next = new_node

    # Your code here

# Your code here

Hint

Print each fruit followed by an arrow until you reach the end, then print None.