Class Variable Access and Assignment

[Antoon Pardon]

Op 2005-11-04, Steven D'Aprano schreef <steve at REMOVETHIScyber.com.au>:
> On Fri, 04 Nov 2005 08:08:42 +0000, Antoon Pardon wrote:
>
>> One other way, to implement the += and likewise operators would be
>> something like the following.
>> 
>> Assume a getnsattr, which would work like getattr, but would also
>> return the namespace where the name was found. The implementation
>> of b.a += 2 could then be something like:
>> 
>>   ns, t = getnsattr(b, 'a')
>>   t = t + 2
>>   setattr(ns, 'a')
>> 
>> 
>> I'm not arguing that this is how it should be implemented. Just
>> showing the implication doesn't follow.
>
> Follow the logical implications of this proposed behaviour.
>
> class Game:
>     current_level = 1
>     # by default, games start at level one  
>     
>     def advance(self):
>         self.current_level += 1
>
>
> py> antoon_game = Game()
> py> steve_game = Game()
> py> steve_game.advance()
> py> steve_game.advance()
> py> print steve_game.level
> 3
> py> print antoon_game.level
>
> What will it print?
>
> Hint: your scheme means that class attributes mask instance attributes.

So? This proposal was not meant to replace the current behaviour.
It was meant to contradict your assertion that some particular
behaviour implied mutable numbers.

My proposal was an example that showed the particular behaviour and
didn't require mutable numbers, so it showed your assertion false.

-- 
Antoon Pardon