[Python-Dev] enum discussion: can someone please summarize open issues?

Steven D'Aprano steve at pearwood.info
Mon Apr 29 07:36:23 CEST 2013

On Sun, Apr 28, 2013 at 09:02:15PM -0700, Ethan Furman wrote:

> Two examples:
>   - the first few integers (up to 256 now, I think) are pre-created by the 
>   interpreter; when you do `int('7')` you are not getting a brand-new, never 
> before used, integer 7 object, you're getting a cached integer 7 object.
>   - all booleans (yup, both of them ;) are pre-created; when you ask for a 
>   True or a False, you are not getting a brand new one.
> Since `is` is discouraged, both of those cases could go the other way 
> (always creating a brand new object) and properly written programs would 
> continue to run just fine -- slower, but fine.
> Enums are the same: they could return brand new instances every time, and 
> programs using `==` to compare will keep on working.  That they don't is an 
> implementation detail.

That's not how I understand it. I expected that the correct way to use 
enums is with identity checks:

if arg is Season.SUMMER: 

At least, that's how I'm used to dealing with sentinels or pseudo-enums 
created with object(), and I just expected it to carry over to actual 
enums. Should I reset my thinking and use == with flufl.enums?


More information about the Python-Dev mailing list