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In this tutorial, we will learn how to implement a doubly linked list in Python.
Implementation of doubly linked list in Python
In the below example we will implementing a doubly linked list in Python:
class Node:
def __init__(self, data):
self.data = data
self.prev = None
self.next = None
class DoublyLinkedList:
def __init__(self):
self.head = None
def append(self, data):
new_node = Node(data)
if self.head is None:
self.head = new_node
else:
current = self.head
while current.next:
current = current.next
current.next = new_node
new_node.prev = current
def prepend(self, data):
new_node = Node(data)
if self.head is None:
self.head = new_node
else:
new_node.next = self.head
self.head.prev = new_node
self.head = new_node
def delete(self, data):
current = self.head
while current:
if current.data == data:
if current.prev:
current.prev.next = current.next
else:
self.head = current.next
if current.next:
current.next.prev = current.prev
return
current = current.next
def display(self):
current = self.head
while current:
print(current.data, end=" ")
current = current.next
print()
# Example usage
dll = DoublyLinkedList()
dll.append(1)
dll.append(2)
dll.append(3)
dll.prepend(4)
dll.delete(2)
dll.display()
This implementation consists of two classes: Node and DoublyLinkedList. The DoublyLinkedList class represents the complete list, but the Node class only represents a single node in the doubly linked list.
The Node class includes three attributes: data, prev, and next, which are used to keep references to the previous and following nodes, respectively.
The DoublyLinkedList class has a single attribute head, which represents the first node in the list. The class offers the following methods for operations on a doubly linked list:
append(data): Appends a new node with the given data at the end of the list.prepend(data): Inserts a new node with the given data at the beginning of the list.delete(data): Removes the first occurrence of a node with the given data from the list.display(): Displays the elements of the list.
In the example usage, we create a DoublyLinkedList object, append some nodes, prepend a node, delete a node, and finally display the elements of the list. The output will be: 4 1 3.