stackLL.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())
stack.display()