On 23/11/2010 15:37, ben.cottr...@nominum.com wrote:
On Tue, 23 Nov 2010 15:15:29 +0000, Michael Foord wrote:
There are still two reasonable APIs (unless you have changed your mind
and think that sticking with plain integers is best), of which I prefer
the latter:
SOME_CONST = Constant('SOME_CONST', 1)
OTHER_CONST = Constant('OTHER_CONST', 2)
or:
Constants = make_constants('Constants', 'SOME_CONST OTHER_CONST', start=1)
SOME_CONST = Constants.SOME_CONST
OTHER_CONST = Constants.OTHER_CONST
I prefer the latter too, because that makes it possible to have
'Constants' be a rendezvous point for making sure that you're
passing something valid. Perhaps using 'in':
def func(foo):
if foo not in Constants:
raise ValueError('foo must be SOME_CONST or OTHER_CONST')
...
I know this is probably not going to happen, but I would *so much*
like it if functions would start rejecting "the wrong kind of 2".
Constants that are valid, integer-wise, but which aren't part of
the set of constants allowed for that argument. I'd prefer not to
think of the number of times I've made the following mistake:
s = socket.socket(socket.SOCK_DGRAM, socket.AF_INET)
Well it would be perfectly possible for the __contains__ method (on the
metaclass so that a Constants class can act as a container) to permit a
*raw integer* (to be backwards compatible with code using hard coded
values) but not permit other constants that aren't valid. Code that is
*deliberately* using the wrong constants would be screwed of course...
All the best,
Michael
~Ben
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