[Python-Dev] PEP 318 - posting draft (original) (raw)

Alex Martelli aleaxit at yahoo.com
Wed Mar 24 15:41:05 EST 2004

On Wednesday 24 March 2004 09:01 pm, Skip Montanaro wrote:

>> class Foo(singleton): >> ... >> Foo = Foo()

Guido> Ok, so the metaclass would have to be a little different, but Guido> this can be done with metaclasses. I'll take your word for it, but I wouldn't have the faintest idea how to do that.

Perhaps something like...:

class metaSingleton(type): def new(cls, classname, classbases, classdict): result = type.new(cls, classname, classbases, classdict) if classbases: return result() else: return result

class singleton: metaclass = metaSingleton

class Foo(singleton): pass

print 'foo is', Foo, 'of type', type(Foo)

which outputs:

foo is <__main__.Foo object at 0x403f968c> of type <class '__main__.Foo'>

...? (As to why one would want such semantics, I dunno -- Singleton being most definitely not my favourite DP, anyway...:-)

Alex

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