[Python-Dev] Pre-pre PEP for 'super' keyword
steve at holdenweb.com
Fri May 4 20:40:26 CEST 2007
Tim Delaney wrote:
> From: "Calvin Spealman" <ironfroggy at gmail.com>
>> I believe the direction my PEP took with all this is a good bit
>> primitive compared to this approach, although I still find value in it
>> because at least a prototype came out of it that can be used to test
>> the waters, regardless of if a more direct-in-the-language approach
>> would be superior.
> I've been working on improved super syntax for quite a while now - my
> original approach was 'self.super' which used _getframe() and mro crawling
> too. I hit on using bytecode hacking to instantiate a super object at the
> start of the method to gain performance, which required storing the class in
> co_consts, etc. It turns out that using a metaclass then makes this a lot
>> However, I seem to think that if the __this_class__ PEP goes through,
>> your version can be simplified as well. No tricky stuffy things in
>> cells would be needed, but we can just expand the super 'keyword' to
>> __super__(__this_class__, self), which has been suggested at least
>> once. It seems this would be much simpler to implement, and it also
>> brings up a second point.
>> Also, I like that the super object is created at the beginning of the
>> function, which my proposal couldn't even do. It is more efficient if
>> you have multiple super calls, and gets around a problem I completely
>> missed: what happens if the instance name were rebound before the
>> implicit lookup of the instance object at the time of the super call?
> You could expand it inline, but I think your second point is a strong
> argument against it. Also, sticking the super instance into a cell means
> that inner classes get access to it for free. Otherwise each inner class
> would *also* need to instantiate a super instance, and __this_class__ (or
> whatever it's called) would need to be in a cell for them to get access to
> it instead.
> BTW, one of my test cases involves multiple super calls in the same method -
> there is a *very* large performance improvement by instantiating it once.
And how does speed deteriorate for methods with no uses of super at all
(which will, I suspect, be in the majority)?
Steve Holden +1 571 484 6266 +1 800 494 3119
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