[Python-ideas] Re: Make dataclass aware that it might be used with Enum

July 18, 2022


      On 7/6/22 17:01, Steve Jorgensen wrote:
...
Perhaps, this has already been addressed in a newer release (?) but in Python 3.9, making
`@dataclass` work with `Enum` is a bit awkward.
Currently, it order to make it work, I have to:
1. Pass `init=False` to `@dataclass` and hand-write the `__init__` method
2. Pass `repr=False` to `@dataclass` and use `Enum`'s representation or write a custom __repr__
Example:
In [72]: @dataclass(frozen=True, init=False, repr=False)
     ...: class Creature(Enum):
     ...:     legs: int
     ...:     size: str
     ...:     Beetle = (6, 'small')
     ...:     Dog = (4, 'medium')
     ...:     def __init__(self, legs, size):
     ...:         self.legs = legs
     ...:         self.size = size
     ...:
In [73]: Creature.Dog
Out[73]: <Creature.Dog: (4, 'medium')>
So why use dataclass then?

class Creature(Enum):
     Beetle = (6, 'small')
     Dog = (4, 'medium')
     def __init__(self, legs, size):
         self.legs = legs
         self.size = size

and
...
...
...
list(Creature)
[<Creature.Beetle: (6, 'small')>, <Creature.Dog: (4, 'medium')>]
...
...
...
Creature.Beetle.size
'small'
...
...
...
Creature.Beetle.legs
6
It looks like dataclass was just making you do a bunch of extra work.

--
~Ethan~

[Python-ideas] Re: Make dataclass aware that it might be used with Enum

Ethan Furman