小屁孩日记 牛奶歌的Python实现

小屁孩日记3里的牛奶歌挺有意思的，和99个瓶子差不多，使用Python实现一下:

# -*- coding: utf-8 -*-

# 小屁孩日记3 牛奶歌 哈哈

from sys import exit

class Song:

    def __init__(self, num_of_bottles):
        self.bottles = num_of_bottles

    def zero(self):
        return self.bottles == 0

    def take_one_down(self):
        if self.bottles != 0:
            self.bottles -= 1
            return str(self.bottles) + (' bottle' if self.bottles == 1 else ' bottles')
                   + ' of the beer.' if self.bottles != 0 else 'No more beer on the wall'

    def sing(self):
        if self.zero():
            raise StopIteration
        else:
            yield str(self.bottles) +  (' bottle' if self.bottles == 1 else ' bottles') + 
                  '  beer on wall, ' 
                  + 'take one down, ' + 'pass it around.' + self.take_one_down()

song = Song(5)
while True:
    try:
        print song.sing().next()
    except Exception:
        exit(0)