'''
Implementation of Stack data structure

'''


class Stack:

    def __init__(self):
	'''
	Initialize stack

	'''
	self.items = []


    def is_empty(self):
	'''
	Return True if stack if empty else False
	
	'''
	return self.item == []


    def push(self, item):
	'''
	Push item to stack

	'''
	self.items.append(item)


    def pop(self):
	'''
	Pop item from stack

	'''
	return self.items.pop()


    def peek(self):
	'''
	Return value of item on top of stack

	'''
	return self.items[-1]

    
    def size(self):
	'''
	Return number of items in stack

	'''
	return len(self.items)

Add Stack data structure