On 5 Jun 2012, at 09:34, Mark Shannon wrote:
> Steven D'Aprano wrote:
>> On Tue, Jun 05, 2012 at 10:20:58AM +0300, Eli Bendersky wrote:
>>> Still, instance of type()" is a bit too cryptic for mere mortals, IMHO.
>> I think that if somebody finds "instance of type" too cryptic, they won't
>> have any chance at all to understand metaclasses.
>> Personally, I think there is a lot confusing about metaclasses, but the idea
>> that classes are instances (objects) is not one of them.
>
> One thing that *is* confusing is that the metaclass parameter in class
> creation is not the metaclass (class of the class), but the class factory.
> For example:
>
> def silly(*args):
> print(*args)
> return int
>
> class C(metaclass=silly):
> def m(self): pass
>
> C () {'m': <function C.m at 0xb721fe14>, '__qualname__': 'C', '__module__':
> '__main__'}
>
> print(C)
> int
>
> In this example the metaclass (ie the class of C) is type (C is int),
> even though the declared metaclass is 'silly'.
>
> I assume it is too late to change the name of the 'metaclass' keyword to
> 'factory', but we could use that terminology in the docs.
Well, the same was always true in Python 2 as well - __metaclass__ could be a
function that was identically "silly". The real "metaclass" (type of the class)
is whatever you use to construct the class.
Michael
>
> Cheers,
> Mark
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