On Apr 22, 2013, at 10:42 AM, Nick Coghlan wrote: >On Mon, Apr 22, 2013 at 10:28 AM, Barry Warsaw <ba...@python.org> wrote: >> On Apr 22, 2013, at 09:02 AM, Nick Coghlan wrote: >> >>>Iteration order matters a lot if you don't want people complaining about >>>enums being broken: >>> >>> class Days(enum.Enum): >>> Monday = 1 >>> Tuesday = 2 >>> Wednesday = 3 >>> Thursday = 4 >>> Friday = 5 >>> Saturday = 6 >>> Sunday = 7 >> >> Sorry, that's still not a complete use case. I don't see why you'd depend >> on iteration order over Days for any particular functionality. > >You mean other than printing the days of the week in order without >needing to worry about the specific values assigned to them?
My point is, "days of the week" has a natural ordering, so why wouldn't you use IntEnum for that? Problem solved. There's no natural ordering for things like colors or animals, so the values don't matter. I claim that neither does the repr or iteration order except that the former should be *predictable* and it would be nice to define the latter, but that's not actually necessary. Undefined iteration order would be just as fine for Enum. >Using sort-by-name also introduces other weirdness, such as subclasses >potentially inserting their values in the middle of inherited names, >rather than appending to the end as one might reasonably expect. I don't see how iteration order could affect how you'd write the derived class syntax. >While using sort-by-name is better than not providing a consistent >ordering at all, using definition order is substantially less >surprising than sorting by key name, and PEP 3115 and >collections.OrderedDict makes that easy to support in Python 3.x. > >The fact that this will make for a behavioural difference between the >standard library and flufl.enum does *not* count as an argument for >making the behaviour of the standard library version less intuitive >(if that was a valid argument, the 3.3+ ipaddress module would look a >*lot* more like it's ipaddr inspiration). Maybe. If they care about iteration order at all, then they will have to special case their code for Python's < 3.3, which means they'll probably have to explicitly sort it anyway for the foreseeable future. I guess it'll be moot in 10 years though. ;) They probably don't care about iteration order, which I think will be the common case (heck, iteration over the enum will be pretty rare *anyway*). -Barry
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