Instance attributes vs method arguments
John O'Hagan
mail at johnohagan.com
Tue Nov 25 05:48:01 EST 2008
On Tue, 25 Nov 2008, Marc 'BlackJack' Rintsch wrote:
> On Tue, 25 Nov 2008 07:27:41 +0000, John O'Hagan wrote:
> > Is it better to do this:
> >
> > class Class_a():
> > def __init__(self, args):
> > self.a = args.a
> > self.b = args.b
> > self.c = args.c
> > self.d = args.d
> > def method_ab(self):
> > return self.a + self.b
> > def method_cd(self):
> > return self.c + self.d
> >
> > or this:
> >
> > class Class_b():
> > def method_ab(self, args):
> > a = args.a
> > b = args.b
> > return a + b
> > def method_cd(self, args)
> > c = args.c
> > d = args.d
> > return c + d
> >
> > ?
> >
> > Assuming we don't need access to the args from outside the class, is
> > there anything to be gained (or lost) by not initialising attributes
> > that won't be used unless particular methods are called?
>
> The question is if `args.a`, `args.b`, …, are semantically part of the
> state of the objects or not. Hard to tell in general.
Would you mind elaborating a little on that first sentence?
>
> I know it's a made up example but in the second class I'd ask myself if
> those methods are really methods, because they don't use `self` so they
> could be as well be functions or at least `staticmethod`\s.
I guess I went overboard keeping the example simple :) : the real case has
many methods, and they all use "self" (except one, actually, so I'm looking
up "static methods" now; thanks).
Regards,
John
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