Python How to Code Linked List: A Comprehensive Guide

Welcome to our comprehensive guide on how to code a linked list in Python. In this tutorial, we will cover everything you need to know about linked lists and how to implement them in Python. Whether you're a beginner or an experienced programmer, this guide will provide you with a solid foundation in linked list concepts and coding techniques.

What is a Linked List?

A linked list is a fundamental data structure in computer science. It is a collection of nodes, where each node contains a value and a reference to the next node in the list. The nodes are connected in a linear fashion, forming a sequence. Unlike arrays, linked lists do not require contiguous memory allocation, making them more flexible and efficient for certain operations.

Creating a Linked List in Python

To create a linked list in Python, we first need to define a Node class. This class will represent each individual node in the linked list. Each node will contain a value and a reference to the next node. Here's an example implementation:

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


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

In the above code, we define a Node class with a constructor that takes a value as an argument. The constructor initializes the value and sets the next reference to None. We also define a LinkedList class with a constructor that initializes the head reference to None. The head reference points to the first node in the linked list.

def insert_at_end(self, value):
    new_node = Node(value)
    if self.head is None:
        self.head = new_node
    else:
        current = self.head
        while current.next is not None:
            current = current.next
        current.next = new_node

In the above code, we first check if the head reference is None, indicating that the linked list is empty. If it is empty, we set the head reference to the new node. Otherwise, we traverse the list by moving from node to node until we reach the last node. Once we reach the last node, we update its next reference to point to the new node.

Insertion at a Specific Position

To insert a new node at a specific position in a linked list, we need to find the node at the desired position and update the next references accordingly. Here's an example implementation:

def insert_at_position(self, value, position):
    if position == 0:
        self.insert_at_beginning(value)
    else:
        new_node = Node(value)
        current = self.head
        count = 0
        while current is not None and count < position - 1:
            current = current.next
            count += 1
        if current is None:
            print('Invalid position')
        else:
            new_node.next = current.next
            current.next = new_node

In the above code, we first check if the desired position is 0. If it is, we call the insert_at_beginning method to insert the new node at the beginning. Otherwise, we create a new node with the given value. We then traverse the list until we reach the node at position - 1. We update the next references of the new node and the current node to insert the new node at the desired position.

Deleting Nodes from a Linked List

Another common operation on a linked list is deletion. There are several ways to delete a node from a linked list, depending on the desired position. Here, we will discuss two common deletion methods: deletion at the beginning and deletion at a specific position.