[Python-Dev] PEP 435 -- Adding an Enum type to the Python standard library

Ethan Furman ethan at stoneleaf.us
Sat Apr 27 20:24:40 CEST 2013

On 04/27/2013 10:35 AM, Guido van Rossum wrote:
> On Sat, Apr 27, 2013 at 10:04 AM, Ethan Furman <ethan at stoneleaf.us> wrote:
>> While this will certainly work, it means you can't have class variables that
>> happen to be the same type as the enum -- so no int in an IntEnum, for
>> example.
>> The solution I like best is the helper class (called, originally enough,
>> enum), and only those items get transformed:
>> class Planet(IntEnum):
>>      MERCURY = enum(1)
>>      VENUS = enum(2)
>>      EARTH = enum(3)
>>      rough_pi = 3     # not transformed
> If this means that the most plain vanilla enum definition still has to
> use the enum(i) notation, I'm against it. Why do you want rough_pi to
> be a class variable anyway? The whole point of an enum is that it's
> *not* a kitchen sink class. An enum for the planets will need other
> support code that doesn't live in the enum class -- it shouldn't be
> considered a general scope for miscellanea. (TBH, I think that using
> classes to scope variables is mostly misguided anyway -- the standard
> mechanism for scoping is the module.)

The two primary use cases I see are the (1) quick give me some names to values so I can fiddle and experiment, and the 
(2) production code with nice docs and the whole shebang.

For (1) I would just use the _make (or whatever it's called) to give me something; for (2) using 'enum()' so that a 
docstring can also be added (even encouraged ;) seems like a Good Thing.

And no, I have no idea what rough_pi is doing there, besides being an example on an int that doesn't get transformed.  ;)


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