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[Python-Dev] Re: Guido's Magic Code was: inline sort option

Phillip J. Eby pje at telecommunity.com
Thu Oct 30 12:51:12 EST 2003 
At 09:16 AM 10/30/03 -0800, Guido van Rossum wrote:
>class PickyClassmethod(classmethod):
>     def __get__(self, obj, cls):
>         if obj is not None:
>             raise TypeError, "class method should be called on class only!"
>         else:
>             return classmethod.__get__(self, None, cls)
>
>I don't want to make this behavior the default behavior, because I
>can see use cases for calling a class method on an instance too,
>knowing that it is a class method; otherwise one would have to write
>the ugly x.__class__.foobar().

If there were a 'classonlymethod()' built-in, I'd probably use it, as I use 
classmethods a fair bit (mostly for specialized constructors), but I don't 
recall ever desiring to call one via an instance.  Do you have an example 
of the use cases you see?

Hm.  What if your PickyClassmethod were a built-in called 'constructor' or 
'factorymethod'?  Probably too confining a name, if there are other uses 
for class-only methods, I suppose.
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