On Fri, Mar 12, 2021 at 1:52 PM Ethan Furman <ethan@stoneleaf.us> wrote:
A question that comes up quite a bit on Stackoverflow is how to test to see if a value will result in an Enum member, preferably without having to go through the whole try/except machinery.

A couple versions ago one could use a containment check:

   if 1 in Color:

but than was removed as Enums are considered containers of members, not containers of the member values.

Maybe you were a bit too quick in deleting it. Was there a serious bug that led to the removal? Could it be restored?
It was also possible to define one's own `_missing_` method and have it return None or the value passed in, but that has also been locked down to either return a member or raise an exception.

At this point I see three options:

1) add a `get(value, default=None)` to EnumMeta (similar to `dict.get()`

But the way to convert a raw value to an enum value is Color(1), not Color[1], so Color.get(1) seems inconsistent.

Maybe you can just change the constructor so you can spell this as Color(1, default=None) (and then check whether that's None)?
2) add a recipe to the docs

But what would the recipe say? Apparently you're looking for a one-liner, since you reject the try/except solution.
3) do nothing

Always a good option. :-) Where's that StackOverflow item? How many upvotes does it have?

--Guido van Rossum (python.org/~guido)