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from __future__ import print_function

__author__ = 'Omkar Pathak'

class Stack(object):

""" A stack is an abstract data type that serves as a collection of

elements with two principal operations: push() and pop(). push() adds an

element to the top of the stack, and pop() removes an element from the top

of a stack. The order in which elements come off of a stack are

Last In, First Out (LIFO).

https://en.wikipedia.org/wiki/Stack_(abstract_data_type)

"""

def __init__(self, limit=10):

self.stack = []

self.limit = limit

def __bool__(self):

return bool(self.stack)

def __str__(self):

return str(self.stack)

def push(self, data):

""" Push an element to the top of the stack."""

if len(self.stack) >= self.limit:

raise StackOverflowError

self.stack.append(data)

def pop(self):

""" Pop an element off of the top of the stack."""

if self.stack:

return self.stack.pop()

else:

raise IndexError('pop from an empty stack')

def peek(self):

""" Peek at the top-most element of the stack."""

if self.stack:

return self.stack[-1]

def is_empty(self):

""" Check if a stack is empty."""

return not bool(self.stack)

def size(self):

""" Return the size of the stack."""

return len(self.stack)

class StackOverflowError(BaseException):

pass

if __name__ == '__main__':

stack = Stack()

for i in range(10):

stack.push(i)

print('Stack demonstration:\n')

print('Initial stack: ' + str(stack))

print('pop(): ' + str(stack.pop()))

print('After pop(), the stack is now: ' + str(stack))

print('peek(): ' + str(stack.peek()))

stack.push(100)

print('After push(100), the stack is now: ' + str(stack))

print('is_empty(): ' + str(stack.is_empty()))

print('size(): ' + str(stack.size()))

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