[Python-ideas] PEP for enum library type?

[Guido van Rossum]

I'm torn. I like the clean look of Tim's:

class Flag(Enum):
   RED, WHITE, BLUE

However, I don't like the magic needed for its implementation -- and
anybody who thinks they know Python pretty well and thinks about this
syntax for more than two seconds has to wonder how on earth it's done
(and the answer is pretty horrible). It is also pretty brittle to
depend on the lookup order -- and I suspect it will be prone to
masking other bugs (any typo in a name used in class-level code will
essentially generate a bogus new enum value).

OTOH I don't like having the string quotes of Antoine's counter-proposal:

class Flag(Enum):
    fields = ('RED', 'WHITE', 'BLUE')

Whenever I see quoted names that are also used unquoted, I cringe a
little (and this includes calls to hasattr() or getattr() with a
string literal for the name).

The compromise that I would personally lean towards is more like this:

class Flag(Enum):
   RED, WHITE, BLUE = <something>

Even if the <something> requires you to know how many values you are
defining, like range(3). If we have to have a somewhat more verbose
syntax that doesn't bother me too much.

FWIW I do like being able to define enums that are ints and strings
(but not mixed); masks/flags I see more as a special case of ints (if
you use this you are likely trying to match some API defined in C or
C++). I also agree that it must be possible to customize the enum
class and the behavior of the values by defining methods on the class.

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