Python/data_structures/stacks/stack.py at master · FrogBattle/Python · GitHub

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from __future__ importprint_function
__author__='Omkar Pathak'


classStack(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):
returnbool(self.stack)

def__str__(self):
returnstr(self.stack)

defpush(self, data):
""" Push an element to the top of the stack."""
iflen(self.stack) >=self.limit:
raiseStackOverflowError
self.stack.append(data)

defpop(self):
""" Pop an element off of the top of the stack."""
ifself.stack:
returnself.stack.pop()
else:
raiseIndexError('pop from an empty stack')

defpeek(self):
""" Peek at the top-most element of the stack."""
ifself.stack:
returnself.stack[-1]

defis_empty(self):
""" Check if a stack is empty."""
returnnotbool(self.stack)

defsize(self):
""" Return the size of the stack."""
returnlen(self.stack)


classStackOverflowError(BaseException):
pass


if__name__=='__main__':
stack=Stack()
foriinrange(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()))