how to make an enum point to a class

Question

Suppose i have this enum for storing all the different Entity types

class Entities(Enum): TREE = auto() ROCK = auto() FLOWER = auto()

I would like to create a function that takes one of these (TREE, ROCK...) enums, and knows that an enum corresponds to a class i have. eg.:

def myFunc(EntityType): return type(EntityType) print(myFunc(Entities.ROCK)) >>>ROCK (where ROCK is an instance of the ROCK class)

and if there is a way to do that, is there one, to maybe even initialise the class eg.:

def myFunc(EntityType): myObj = EntityType(pos=(0,0)) return myObj

Kyle Parsons · Accepted Answer · 2021-09-05 16:28:28Z

What if you just ditch the auto and use the classes themselves as the values of Entities? Suppose Tree, Rock, and Flower are the names of your classes:

class Entities(Enum): TREE = Tree ROCK = Rock FLOWER = Flower

Here Entities.TREE.value is the class constructor for Tree.

This won't really help to initialize anything unless all the targets have identical initializers.

jvllmr · Accepted Answer · 2021-09-05 16:32:50Z

Here an example to Kyle Parsons' answer:

from enum import Enum from dataclasses import dataclass @dataclass class Animal: name: str age: int type: str = None @dataclass class Cat(Animal): type: str = 'Cat' @dataclass class Dog(Animal): type: str = 'Dog' class AnimalType(Enum): DOG = Dog CAT = Cat def get_animal(type: Enum, name: str, age: int): return type.value(name, age) print(get_animal(AnimalType.CAT, 'Peter', 12))

This just emphasizes that all the target types have to have identical constructors.

Mad Physicist · Accepted Answer · 2021-09-08 01:42:12Z

You can add attributes to an Enum object, or you can map an Enum using a dict. There are other options as well, but these seem simplest.

Let's say you have classes Tree, Rock, Flower, etc, corresponding to the values of the Enum:

class Tree: def __init__(self, height, coords): pass class Rock: def __init__(self, coords): pass class Flower: def __init__(self, color, iscarnivore, coords): pass

I've specifically shown an extended version, where each class has a different initializer, and a different set of defaults. If they are all the same, use the existing answers.

Option 1 is to define the enum like this:

class Entities(Enum): TREE = (Tree, 100, (0, 0)) ROCK = (Rock, (0, 0)) FLOWER = (Flower, 'red', True, (0, 0)) def __new__(cls, t, *args): obj = object.__new__(cls) obj._value_ = len(cls.__members__) + 1 obj.type = t obj.defaults = args return obj def init(self): return self.type(*self.defaults)

Now, my_func is just the init method of the enum itself:

>>> FLOWER.init() # Calls Flower('red', False, (0, 0))

The second option would be to map the Enum members to the class:

cmap = { Entitites.TREE: (Tree, 100, (0, 0)), Entitites.ROCK: (Rock, (0, 0)), Entitites.FLOWER: (Flower, 'red', True, (0, 0)), } def my_func(entity): t, *args = cmap[entity] return t(*args)

Collectives™ on Stack Overflow

how to make an enum point to a class

3 Answers 3

1 Comment

1 Comment

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

1 Comment

Comments

Related