Python Program to Reverse a Stack using Recursion

When it is required to reverse a stack data structure using recursion, a ‘stack_reverse’ method, in addition to methods to add value, delete value, and print the elements of the stack are defined.

Below is a demonstration of the same −

Example

class Stack_structure:
   def __init__(self):
      self.items = []

   def check_empty(self):
      return self.items == []

   def push_val(self, data):
      self.items.append(data)

   def pop_val(self):
      return self.items.pop()

   def print_it(self):
      for data in reversed(self.items):
         print(data)

def insert_bottom(instance, data):
   if instance.check_empty():
      instance.push_val(data)
   else:
      deleted_elem = instance.pop_val()
      insert_bottom(instance, data)
      instance.push_val(deleted_elem)

def stack_reverse(instance):
   if not instance.check_empty():
      deleted_elem = instance.pop_val()
      stack_reverse(instance)
      insert_bottom(instance, deleted_elem)

my_instance = Stack_structure()
data_list = input('Enter the elements to add to the stack: ').split()
for data in data_list:
   my_instance.push_val(int(data))

print('The reversed stack is:')
my_instance.print_it()
stack_reverse(my_instance)
print('The stack is:')
my_instance.print_it()

Output

Enter the elements to add to the stack: 23 56 73 81 8 9 0
The reversed stack is:
0
9
8
81
73
56
23
The stack is:
23
56
73
81
8
9
0

Explanation

A ‘Stack_structure’ class is created that initializes an empty list.
A ‘check_empty’ method is defined to see if a stack is empty.
Another method named ‘push_val’ is defined that adds elements to the stack.
Another method named ‘pop_val’ is defined that deletes elements from the stack.
A method named ‘print_it’ is defined that helps print the elements of the stack.
A method named ‘insert_bottom’ is defined, that adds element to the bottom of the stack, instead of adding to the top by default.
Another method named ‘stack_reverse’ is defined, that helps reverse a given stack.
An instance of this ‘Stack_structure’ is defined.
The elements of stack are taken from the user.
It is iterated over, and methods are called to add value to the stack and print it on the console.
Now, the ‘stack_reverse’ is called on this list.
The ‘print_it’ is called to display the reversed stack on the console.