wat.py

class Cat(object):
    def __init__(self):
        self.tummy = []

    def eat(self, thing):
        self.tummy.append(thing)

    def hairball(self):
        print("I puked up a {}".format(self.tummy.pop()))

snowball = Cat()
snowball.eat('fish')
snowball.eat('shoelace')

snowball.hairball()
snowball.hairball()

# I puked up a shoelace
# I puked up a fish