activestate上面有篇文章Singleton? We don't need no stinkin' singleton: the Borg design pattern, 告诉我们Borg模式要比单例模式要好。 为什么这样说：单例模式生成的单例一旦生成就一直存在，但是Borg确实和源共享的能修改
class Config(object):
_we_are_one = {}
_myvalue = ""
def __new__(cls, *p, **k):
self = object.__new__(cls, *p, **k)
self.__dict__ = cls._we_are_one
return self
def myvalue(self, value=None):
if value:
self._myvalue = value
return self._myvalue
if __name__ == '__main__':
conf = Config()
conf.myvalue("Hello")
conf2 = Config()
print conf2.myvalue()
不要惊讶，其实是因为在修改myvalue的时候不仅修改了conf.__dict__还修改了Config._we_are_one，所以…
然后还有个装饰器版本：
def borg(cls):
cls._state = {}
orig_init = cls.__init__
def new_init(self, *args, **kwargs):
self.__dict__ = cls._state
orig_init(self, *args, **kwargs)
cls.__init__ = new_init
return cls
@borg
class TestBorg(object):
def say_borg(self):
print "i am borg"