Classes as namespaces?
J. Clifford Dyer
jcd at sdf.lonestar.org
Sat Mar 27 13:04:59 CET 2010
On Fri, Mar 26, 2010 at 02:49:02PM +0000, kj wrote regarding Classes as namespaces?:
> What's the word on using "classes as namespaces"? E.g.
> class _cfg(object):
> spam = 1
> jambon = 3
> huevos = 2
> breakfast = (_cfg.spam, _cfg.jambon, _cfg.huevos)
> Granted, this is not the "intended use" for classes, and therefore
> could be viewed as a misuse ("that's what dictionaries are for",
> etc.). But other than this somewhat academic objection[*], I really
> can see no problem with using classes in this way.
> And yet, I've come across online murky warnings against using
> classes as "pseudo-namespaces". Is there some problem that I'm
> not seeing with this technique?
I don't see anything wrong with this, except that I would clean it up in a couple ways. Like other posters, I would give the class a proper class name (Cfg).
I also would not assign integers to spam, jambon, or huevos. Instead I would assign each a bare object(). That way you won't get unexpected interactions with other constants outside the class. An object() is equal only to itself.
I would also not rule out letting your "pseudo-namespace" grow into a full-fledged class. If you've got a method that makes sense with your class, use it.
spam = object()
jambon = object()
huevos = object()
def get_animal(self, meat):
if meat == self.jambon:
elif meat == self.huevos:
elif meat = self.spam:
Later, perhaps, you might refactor so that each meat type (OK so huevos aren't a meat) gets its own subclass, with a simple, one-line get_animal method.
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