Since I started learning some Rust and getting to know its enums, I've been very into using Enum
s in Python. And while enums in both languages are very different, they're close enough for most of my current use cases. Moreover, within Python, Enum
s are used in frameworks like Typer
(CLI) and FastAPI
(API), where they are used to provide validation to input within a set of possibilities.
In Python, an Enum
without explicit member values is created as follows
from enum import Enum, auto
class Color(Enum):
RED = auto()
BLUE = auto()
GREEN = auto()
list(Color)
# [<Color.RED: 1>, <Color.BLUE: 2>, <Color.GREEN: 3>]
or alternatively, using a functional API
from enum import Enum
Animal = Enum('Animal', 'ANT BEE CAT DOG', module=__name__)
list(Animal)
# [<Animal.ANT: 1>, <Animal.BEE: 2>, <Animal.CAT: 3>, <Animal.DOG: 4>]
Great! The problem is that when having Enum
s that interface with external users, the integer values of the members are of little use and very uninformative.
That's why I tend to prefer to use a different way, where the values are strings.
class Animal(str, Enum):
ANT = 'ant'
BEE = 'bee'
CAT = 'cat'
DOG = 'dog'
list(Animal)
# [<Animal.ANT: 'ant'>,
# <Animal.BEE: 'bee'>,
# <Animal.CAT: 'cat'>,
# <Animal.DOG: 'dog'>]
Now, attending to the real problem at hand hinted at by the title. I had a rather long set of about 15 possible elements, and I didn't want to manually create all the elements of the Enum
myself in a way that the values are informative. That's the exact thing we try to avoid, repetitive manual work.
We already saw the functional API work with an iterable, so basically, the problem is already solved. However, it does in a way that the member values are uninformative.
The solution is to provide a dictionary instead of a list (or a string in the example). Then, the (keys, value) pairs of the dictionary become the member name and value of the Enum
as shown below. Going from a list (or an iterable) to a dictionary is straightforwardly achieved with a dictionary comprehension.
Animal = Enum('Animal', {el:el.lower() for el in 'ANT BEE CAT DOG'.split(" ")}, type=str)
list(Animal)
# [<Animal.ANT: 'ant'>,
# <Animal.BEE: 'bee'>,
# <Animal.CAT: 'cat'>,
# <Animal.DOG: 'dog'>]
Which accomplishes what I was going for.
Top comments (1)
Came across this post while researching ways to dynamically create enum from another enum's key values.
The same document helped: enum members can be accessed and iterated over with
__members__
attribute: