Class Variable Access and Assignment

[Mike Meyer]

bokr at oz.net (Bengt Richter) writes:
> On Thu, 03 Nov 2005 13:37:08 -0500, Mike Meyer <mwm at mired.org> wrote:
> [...]
>>> I think it even less sane, if the same occurce of b.a refers to two
>>> different objects, like in b.a += 2
>>
>>That's a wart in +=, nothing less. The fix to that is to remove +=
>>from the language, but it's a bit late for that.
>>
> Hm, "the" fix? Why wouldn't e.g. treating augassign as shorthand for a source transformation
> (i.e., asstgt <op>= expr  becomes by simple text substitution asstgt = asstgt <op> expr)
> be as good a fix? Then we could discuss what
>
>     b.a = b.a + 2
>
> should mean ;-)

The problem with += is how it behaves, not how you treat it. But you
can't treat it as a simple text substitution, because that would imply
that asstgt gets evaluated twice, which doesn't happen.

> OTOH, we could discuss how you can confuse yourself with the results of b.a += 2
> after defining a class variable "a" as an instance of a class defining __iadd__ ;-)

You may confuse yourself that way, I don't have any problems with it
per se.

> Or point out that you can define descriptors (or use property to make it easy)
> to control what happens, pretty much in as much detail as you can describe requirements ;-)

I've already pointed that out.

     <mike
-- 
Mike Meyer <mwm at mired.org>			http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.