stack in gfg

1# Python program for linked list implementation of stack
2
3# Class to represent a node
4
5
6class StackNode:
7
8	# Constructor to initialize a node
9	def __init__(self, data):
10		self.data = data
11		self.next = None
12
13
14class Stack:
15
16	# Constructor to initialize the root of linked list
17	def __init__(self):
18		self.root = None
19
20	def isEmpty(self):
21		return True if self.root is None else False
22
23	def push(self, data):
24		newNode = StackNode(data)
25		newNode.next = self.root
26		self.root = newNode
27		print "% d pushed to stack" % (data)
28
29	def pop(self):
30		if (self.isEmpty()):
31			return float("-inf")
32		temp = self.root
33		self.root = self.root.next
34		popped = temp.data
35		return popped
36
37	def peek(self):
38		if self.isEmpty():
39			return float("-inf")
40		return self.root.data
41
42
43# Driver code
44stack = Stack()
45stack.push(10)
46stack.push(20)
47stack.push(30)
48
49print "% d popped from stack" % (stack.pop())
50print "Top element is % d " % (stack.peek())
51
52