stack_node.py

# Python programe for linked list implementation
# Class to represent a node
class StackNode:

    # Constructor to initialize a node
    def __init__(self, data):
        self.data = data
        self.next = None

class Stack:

    # Constractor to initialize the root of linked list
    def __init__(self):
        self.root = None

    def is_empty(self):
        return True if self.root is None else False

    def push(self, data):
        new_node = StackNode(data)
        new_node.next = self.root
        self.root = new_node
        print("%d pushed to stack" %(data))

    def pop(self):
        if self.is_empty():
            return float("-inf")

        temp = self.root
        self.root = self.root.next
        popped = temp.data

        return popped

    def peek(self):
        if self.is_empty():
            return float("-inf")

        return self.root.data


# Driver program to test above class
stack = Stack()
stack.push(10)
stack.push(20)
stack.push(30)

print("%d popped from stack." %stack.pop())
print("Top element is %d " %stack.peek())