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....
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