Python Program to Implement a Stack using Linked List

When it is required to implement a stack data structure using a linked list, a method to add (push values) elements to the linked list, and a method to delete (pop values) the elements of the linked list are defined.

Below is a demonstration for the same −

Example

 Live Demo

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

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

   def push_val(self, data):
      if self.head is None:
         self.head = Node(data)
      else:
         newNode = Node(data)
         newNode.next = self.head
         self.head = newNode

   def pop_val(self):
      if self.head is None:
         return None
      else:
         del_Val = self.head.data
         self.head = self.head.next
         return del_Val

my_instance = Stack_structure()
while True:
   print('push <value>')
   print('pop')
   print('quit')
   my_input = input('What action would you like to perform ? ').split()

   operation = my_input[0].strip().lower()
   if operation == 'push':
      my_instance.push_val(int(my_input[1]))
   elif operation == 'pop':
      del_Val = my_instance.pop_val()
      if del_Val is None:
         print('The stack is empty.')
      else:
         print('The deleted value is : ', int(del_Val))
   elif operation == 'quit':
      break

Output

push <value>
pop
quit
What action would you like to perform ? push 56
push <value>
pop
quit
What action would you like to perform ? push 78
push <value>
pop
quit
What action would you like to perform ? push 90
push <value>
pop
quit
What action would you like to perform ? pop
The deleted value is : 90
push <value>
pop
quit
What action would you like to perform ? quit

Explanation

• The ‘Node’ class is created.

• Another ‘Stack_structure’ class with required attributes is created.

• It has an ‘init’ function that is used to initialize the first element, i.e the ‘head’ to ‘None’.

• A method named ‘push_val’ is defined, that helps add a value to the stack.

• Another method named ‘pop_val’ is defined, that helps delete a value from the top of the stack, and returns the deleted value.

• An instance of the ‘Stack_structure’ is created.

• Three options are given, such as ‘push’, ‘pop’, and ‘quit’.

• The ‘push’ option adds a specific value to the stack.

• The ‘pop’ option deletes the topmost element from the stack.

• The ‘quit’ option comes out of the loop.

• Based on the input/choice by user, the respective operations are performed.

• This output is displayed on the console.