On Tue, 25 Nov 2008, Rafe wrote: > On Nov 25, 5:48 pm, John O'Hagan <[EMAIL PROTECTED]> wrote: > > 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 > > I'm not sure if you are asking a technical question or a design > question. If it helps, I try to think of an object as a thing which > has a job to do. If the 'thing' needs information every time to define > what it is, or give it a starting state, then that is an argument of > __init__() . If I want the object to change or handle something which > is a logical task of 'thing', then I give it what it needs via > properties or methods (I find I almost never use "public" instance > attributes, but then again I am usually writing SDKs which is all > about interface). > > Not sure if that helps... > You've picked up my fundamental confusion! Thanks to your reply and others I think that's cleared up for me now, which just leaves the technical question: insofar as one is only interested in accessing methods, is there an difference in efficiency (for large enough number of methods and arguments) between
a) passing all arguments to __init__() and accessing them via self within individual methods: class = Class(all_class_args) class.method_a() class.method_b() ... or b) passing the arguments needed by each method when it is called on an instance: class = Class() class.method_a(a_args) class.method_b(b_args) ... Thanks to all, John -- http://mail.python.org/mailman/listinfo/python-list
