On 2 May 2013 02:46, "Guido van Rossum"
On Wed, May 1, 2013 at 9:18 AM, Tres Seaver
wrote: I'd be glad to drop both of those in favor of subclassing: I think the emphasis on "class-ness" makes no sense, given the driving usecases for adopting enums into the stdlib in the first place. IOW, I would vote that real-world usecases trump hypothetical purity.
Yeah, this is the dilemma. But what *are* the real-world use cases? Please provide some.
Here's how I would implement "extending" an enum if subclassing were not allowed:
class Color(Enum): red = 1 white = 2 blue = 3
class ExtraColor(Enum): orange = 4 yellow = 5 green = 6
flag_colors = set(Color) | set(ExtraColor)
Now I can test "c in flag_colors" to check whether c is a flag color. I can also loop over flag_colors. If I want the colors in definition order I could use a list instead:
ordered_flag_colors = list(Color) + list(ExtraColor)
But this would be less or more acceptable depending on whether it is a common or esoteric use case.
If enums had an "as_dict" method that returned an ordered dictionary, you could do: class MoreColors(Enum): locals().update(Colors.as_dict()) orange = 4 ... Using a similar API to PEP 422's class initialisation hook, you could even simplify that to: class MoreColors(Enum, namespace=Colors.as_dict()): orange = 4 ... Cheers, Nick.
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