Stack.py

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

class Stack:
    def __init__(self,value):
        new_node = Node(value)
        self.bottom = new_node
        self.top = new_node
        self.height = 1
 
    def print_stack(self):
        temp = self.top
        while temp is not None:
            print(temp.value)
            temp = temp.next

    
    def push(self, value):
        new_node = Node(value)
        if self.height == 0:
            self.top = new_node
        else:
            new_node.next = self.top
            self.top = new_node
        self.height += 1
    
    def pop(self):  
        if self.height == 0:
            return None
        temp = self.top
        self.top = self.top.next
        temp.next = None
        self.height -= 1
        return temp
    
mainStack = Stack(4)
mainStack.push(3)
mainStack.push(2)
mainStack.push(1)

print('Stack before pop():')
mainStack.print_stack()

print('\nPopped node:')
print(mainStack.pop().value)

print('\nStack after pop():')
mainStack.print_stack()