Mike Lundy added the comment:
@serhiy.storchaka: It's somewhat of a special case, to be sure. However, I do
think it's justified to put it into the base (rather than a user type) for
three reasons:
1) It makes IntEnum and Enum consistent. IntEnum actually already handles this
case just fine, because it's an int and therefore already supports __bool__
correctly. It feels odd that changing the storage format from an IntEnum to a
Enum should break the logic- correctly used, the actual enum values should
never matter. This small change just brings them into line.
2) It is less surprising than the current case; I discovered this when I did
something like the Enum.Nope case here, and I naively used the enum in an if
statement, assuming that the value would control the __bool__ value. (This was
caught by my tests, of course, but the point remains that I wrote the code).
Normally in python, you'd expect the default bool conversion to be
unconditionally True, but enums aren't really normal objects; for any use case
for which there is a default noop value, you'd generally put that value _into_
the enum:
class FilterType(Enum):
NONE = None
SUB = 'Sub'
UP = 'Up'
...
3) It's not logically inconsistent with the idea of Enums. The other dunder
methods you mention aren't consistent with the concept: __float__ (enum values
aren't generally numbers except as an implementation detail), __lt__ (enums
aren't generally ordered), __len__ (enums aren't generally containers). The one
thing an enum does have is a value, and it feels consistent to me to check the
truthiness of an enum without having to reach into the .value to do so.
Anyway, that's my case for inclusion!
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<http://bugs.python.org/issue24840>
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