Enum + new in 3.11

[Thomas Passin]

On 6/16/2023 1:40 AM, dn via Python-list wrote:
> Have you figured-out a use for the @enum.member and @enum.nonmember 
> decorators (new in Python 3.11)?
> 
> 
> "What's New" says:
> Added the member() and nonmember() decorators, to ensure the decorated 
> object is/is not converted to an enum member.
> 
> The PSL docs say:
> @enum.member
>      A decorator for use in enums: its target will become a member.
> 
> also:
> enum members have names and values (the name of Color.RED is RED, the 
> value of Color.BLUE is 3, etc.)
> 
> Whereas the "Utilities and Decorators" section is slightly confusing 
> because class decorators are mixed with others, so one has to read 
> more-carefully.
> 
> 
> "Curiosity killed the cat" and other cautionary tales/tails...
> 
> Have added the following decorated staticmethod to a basic enum. It is 
> indeed recognised as a member of the enum, but its value is the 
> method-object. To gain the value the method-object represents 
> (property-like behavior) one has to call the method/enum-value as a 
> function:-
> 
> 
> from enum import Enum, member
> 
> 
> class MenuOptions( Enum ):
>      """ Legal menu-choices. """
>      N = "NewGame"
>      L = "LoadGame"
>      # ...
> 
>      @member
>      @staticmethod
>      def extra_member()->str:
>          return "QuitGame"
> 
> 
> def print_demo( enum_chosen:MenuOptions )->None:
>      """ Illustrative printing. """
>      print( "Name:", enum_chosen, enum_chosen.name )
>      if isinstance( enum_chosen, MenuOptions ):
>          print( "Value:", enum_chosen.value )
> 
> 
> print( MenuOptions.__members__ )
> # {'N': <MenuOptions.N: 'NewGame'>, 'L': <MenuOptions.L: 'LoadGame'>, 
> 'extra_member': <MenuOptions.extra_member: <staticmethod(<function 
> MenuOptions.extra_member at 0x7f0802128860>)>>}
> 
> print_demo( MenuOptions[ "L" ] )
> # Name: MenuOptions.L L
> # Value: LoadGame
> 
> print_demo( MenuOptions.extra_member )
> # Name: MenuOptions.extra_member extra_member
> # Value: <staticmethod(<function MenuOptions.extra_member at 
> 0x7f0802128860>)>
> 
> print( MenuOptions.extra_member.value() )
> # QuitGame
> 
> 
> Therefore, like an @property decorator applied to a method in a 
> custom-class, it could be used to only evaluate some 'expensive' 
> computation if/when it is needed. Similarly, it could use the other 
> values within the enum in order to present some 'combination'.
> 
> Weirdly (given that enums are considered immutable) I imagine that if 
> the 'extra_member' were to call some external function with varying 
> output, the value could be considered mutable when it is eventually called.
> 
> Other?better ideas...

mypy is having trouble with 3.11 enums:

"There are 83 open Enum mypy issues at the the time of this writing.

Getting the Enum datatype to work with mypy is becoming impossible as I 
find myself having to use cast() in at least every other line."

(see https://github.com/python/mypy/issues/12841)

There have also been other changes to enum  in 3.11 - here is a useful 
rundown:

https://www.andy-pearce.com/blog/posts/2023/Jan/whats-new-in-python-311-new-and-improved-modules/#enum

I had no idea....