Guido's new method definition idea

Daniel Fetchinson fetchinson at googlemail.com
Sun Dec 7 20:39:43 CET 2008


>>>> The story of the explicit self in method definitions has been
>>>> discussed to death and we all know it will stay. However, Guido
>>>> himself acknowledged that an alternative syntax makes perfect sense
>>>> and having both (old and new) in a future version of python is a
>>>> possibility since it maintains backward compatibility. The alternative
>>>> syntax will be syntactic sugar for the old one. This blog post of his
>>>> is what I'm talking about:
>>>>
>>>> http://neopythonic.blogspot.com/2008/10/why-explicit-self-has-to-stay.html
>>>>
>>>> The proposal is to allow this:
>>>>
>>>> class C:
>>>>     def self.method( arg ):
>>>>         self.value = arg
>>>>         return self.value
>>>>
>>>> instead of this:
>>>>
>>>> class C:
>>>>     def method( self, arg ):
>>>>         self.value = arg
>>>>         return self.value
>>>>
>>>> I.e. explicit self stays only the syntax is slightly different and may
>>>> seem attractive to some. As pointed out by Guido classmethods would
>>>> work similarly:
>>>>
>>>> class C:
>>>>     @classmethod
>>>>     def cls.method( arg ):
>>>>         cls.val = arg
>>>>         return cls.val
>>>>
>>>> The fact that Guido says,
>>>>
>>>> "Now, I'm not saying that I like this better than the status quo. But
>>>> I like it a lot better than [...] but it has the great advantage that
>>>> it is backward compatible, and can be evolved into a PEP with a
>>>> reference implementation without too much effort."
>>>>
>>>> shows that the proposal is viable.
>>>>
>>>> I'd like this new way of defining methods, what do you guys think?
>>>> Anyone ready for writing a PEP?
>>>>
>>> What's the advantage?  If there is not a good reason, I would strongly
>>> opposed polluting the language.
>>
>> Did you read the blog post? The advantage is having a less confusing
>> situation for newbies
>
> Once again: how is adding "magical" syntax going to reduce confusion ?
>
>> (confusing the number of arguments to a method
>> call).
>
> This is only confusing the first time. The correct solution to this
> problem is IMHO to better document Python's object model, specially how
> the descriptor protocol turns functions into methods.

As I've said in another reply the argument that "def self.meth( arg )"
is confusing because "self" doesn't exist in the current scope as an
instance is convincing to me. So I no longer like the alternate syntax
mentioned by Guido.

Still, improved error messages would be desirable (concerning the
number of arguments passed to an instance method).

Cheers,
Daniel

-- 
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