[Python-Dev] [Python-checkins] peps: Pre-alpha draft for PEP 435 (enum). The name is not important at the moment, as (original) (raw)

Stephen J. Turnbull stephen at xemacs.org
Tue Feb 26 10:29:00 CET 2013

Ethan Furman writes:

sjt wrote:

Note that in both counting and listing the object of the operation is not an element. It is a set, and set membership is the most important aspect of the elements for that purpose.

No, it isn't. It may be in some cases.

I'm referring only to the dictionary definitions you quote.

It really sounds to me like your use case (and even more so, Antoine's) would be perfectly well-served by a named constant class that doesn't know anything about enumerability.

My enums even respect it to the point of not comparing equal to different enum sets. But, quite frankly, it's the enum's ability to let me use a name to mean a number that is the most important. And the most important thing for the Enum class is to assign those numbers for me as automatically as possible.

But "mean a number" and "assigned automatically" are close to mutually exclusive (except that "as possible" gives you a lot of wiggle room).

That is, if by "name means number" you imply that the numbers have semantics (as in Antoine's HTTP status code example), you care what the numbers are, and they can't be assigned automatically.

OTOH, if the numbers are assigned very automatically (ie, completely implicitly), I have trouble with coming up with a use case where ability to use integer arithmetic (including comparisons other than equality and set membership) on them by default is anything but a trap. Eg, with a Likert scale for preference[1], I do want to order them, but (at least when I'm teaching statistics) I really don't want them added and subtracted without thinking about exactly what the operation means.

And if you really need arithmetic and automatic assignment is good enough, what's wrong with their ordinary names (ie, 1, 2, 3, ...)?

Footnotes: [1] A qualitative expression of strength of feeling ("hate" = 1, "dislike" = 2, "indifferent" = 3, "like" = 4, "love" = 5).

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