stacks in gfg code example

Example: stack in gfg

# Python program for linked list implementation of stack

# Class to represent a node


class StackNode:

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


class Stack:

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

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

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

	def pop(self):
		if (self.isEmpty()):
			return float("-inf")
		temp = self.root
		self.root = self.root.next
		popped = temp.data
		return popped

	def peek(self):
		if self.isEmpty():
			return float("-inf")
		return self.root.data


# Driver code
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())