Alex Popescu <[EMAIL PROTECTED]> wrote in news:[EMAIL PROTECTED]:
> "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote in > news:[EMAIL PROTECTED]: > >> Alex Popescu schrieb: >>> Hi all! >>> >>> I was reading through Python Cookbook the Singleton recipe. At this >>> moment I am a bit puzzled as the example in the book is not working >>> resulting in: >>> >>> TypeError: type.__new__(SingleSpam): SingleSpam is not a subtype of >>> type >>> >>> (I haven't presented the original code as I am not sure about >>> copyrights). >> >> AFAIK the cookbook is completely found online at ASPN. So no sweat >> publishing it here. >> >> >> And regarding the problem: is it possible that you forgot to subclass >> SingleSpam from object? >> >> Diez > > The exact code: > class Singleton(object): > """ A Pythonic Singleton """ > def _ _new_ _(cls, *args, **kwargs): > if '_inst' not in vars(cls): > cls._inst = type._ _new_ _(cls, *args, **kwargs) > return cls._inst > > if _ _name_ _ == '_ _main_ _': > class SingleSpam(Singleton): > def _ _init_ _(self, s): self.s = s > def _ _str_ _(self): return self.s > s1 = SingleSpam('spam') > print id(s1), s1.spam( ) > s2 = SingleSpam('eggs') > print id(s2), s2.spam( ) > > ./alex > -- > .w( the_mindstorm )p. > I got it working in 2 ways: class Singleton(object): """ A Pythonic Singleton """ def __new__(cls, *args, **kwargs): if '_singletoninstance' not in vars(cls): #variant 1: cls._singletoninstance = object.__new__(cls, *args, **kwargs) #variant 2: cls._singletoninstance = super(type, cls).__new__(cls, *args, **kwargs) return cls._singletoninstance Both of these seem to work. ./alex -- .w( the_mindstorm )p. -- http://mail.python.org/mailman/listinfo/python-list
