标签：
1. @classmethod and @staticmethod
http://stackoverflow.com/questions/12179271/python-classmethod-and-staticmethod-for-beginner
2. yield
http://stackoverflow.com/questions/231767/what-does-the-yield-keyword-do-in-python
标签：
原文地址：http://www.cnblogs.com/phoenix13suns/p/4681735.html
