Using metaclasses to play with decorators.

David MacQuigg dmq at gain.com
Wed Jun 23 23:51:53 CEST 2004


On Wed, 23 Jun 2004 07:30:34 -0400, "Colin J. Williams"
<cjw at sympatico.ca> wrote:

>
>
>David MacQuigg wrote:
>> On Sun, 20 Jun 2004 14:48:23 -0400, "Colin J. Williams"
>> <cjw at sympatico.ca> wrote:
>> 
>> 
>>>I have yet to wrap my mind around decorators.
>> 
>> 
>> Decorators are very simple.  They are just a way to provide different
>> forms of methods, without introducing a new keyword, or some other
>> more awkward syntax.
>> 
>> Say you wanted to define a method that didn't have 'self' as its first
>> argument.  You could add a new keyword to the language:
>> 
>> noself methodA(x,y):
>> 	return x + y
>> 
>> Or you could add a "decorator" to the existing syntax:
>> 
>> def methodA(x,y) [noself]:
>> 	return x + y
>> 
>> Change 'noself' to 'staticmethod' and you have one of the current
>> proposals in PEP318.
>> 
>> Don't get distracted by 'staticmethod' and other mumbo-jumbo
>> terminology, and you should have no problem with decorators.
>
>OK, I'll ignore 'staticmethod', but could you tell me how
>
>   def methodA(x, y) [noself]:
>     return x + y
>
>differs in substance from
>
>   def methodA(self, y):
>     return self + y
>
>or
>   def methodA(x, y):
>     return x + y
>
>What has been gained by the added syntactic clutter?

The example above was to explain decorators, not justify them.  If
they were to be used *only* to clean up the current syntax for
staticmethod, then I would say a better alternative would be to get
rid of the need for a separate staticmethod form entirely. ( See the
thread "Unification of Methods and Functions" for a thorough
discussion of this topic.)

Are decorators on functions necessary?  I can't think of a simpler or
more consistent way to handle all the variations proposed in PEP 318.

Assuming that we *will* have a decorator syntax with many options, I
think that making [staticmethod] one of those options is appropriate.
I would still prefer a word more meaningful to new users, however. The
rational I have heard for "staticmethod" is so contorted, it is not
worth repeating.

-- Dave




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