CLASS NODE.py

class Node:
    def _init_(self,data):
        self.data=data
        self.next=None
        
class stack:
    def _init_(self):
        self.head=None
        
    def is_empty(self):
        return self.head is None
    def push(self,data):
        new_node=Node(data)
        new_node.next=self.head
        self.head=new_node
    def pop(self):
        if self.is_empty():
            return None
        popped=self.head.data
        self.head=self.head.next
        return popped
    def peek(self):
        if  self.is_empty():
            return None
        return self.head.data
    def display(self):
        current=self.head
        while current:
            print(current.data,end="->")
            current=current.next
        print("None")
        
stack=stack()
stack.push(1)
stack.push(2)
stack.push(3)
stack.display()
print("popped:",stack.pop())
print("peek:",stack.peek())