[Python-Dev] PEP 435 -- Adding an Enum type to the Python standard library (original) (raw)
Guido van Rossum guido at python.org
Sat Apr 27 19:30:50 CEST 2013
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On Sat, Apr 27, 2013 at 9:41 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
On Sun, Apr 28, 2013 at 2:11 AM, Larry Hastings <larry at hastings.org> wrote:
On 04/26/2013 02:41 PM, Guido van Rossum wrote:
I am still optimistic that we can come up with a rule that works well enough in practice (and the Zen rule to which I was referring was, of course, "practicality beats purity").
The rule I liked best is "ignore callables, descriptors, and anything with leading & trailing double underscores". Personally I'd modify that to simply "anything with two leading underscores" so you can have private variables. It seems Pythonic to me in that classes already treat all those things special. And if you want enums of any of those things you can instantiate & insert them by hand after the class definition. Does that fail in an important way? Nope, those cover it.
Great, sounds like a plan. The exception for callables may not even be needed -- the callables we care about (and some non-callables, like properties) are all descriptors. Or do we care about nested class definitions? (The reason I'm not keen on a general exemption for callables is that some 3rd party objects you wouldn't necessarily expect to be callable actually are.)
I agree on a general exemption for dunder names. The problem with exempting __private is that by the time the metaclass sees them, they've already been mangled to _classname__private. And I could just about imagine a use case for having a private value in an enum.
-- --Guido van Rossum (python.org/~guido)
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