Using the enum macro

The enum macro provides a significantly more powerful alternative to the python enum module. First, create a file called enum.mpy. This is where we will be experimenting with the enum. It should have the following contents:

macro import enum

enum Animals:
    Dog
    Cat
    Bird
    Other(name: str)

This file will be converted to the following code:

# Macro imported: enum

class Animals:
    def __assign_enum_types__(Animals, dog, cat, bird, other):
        Animals.Dog = dog
        Animals.Cat = cat
        Animals.Bird = bird
        Animals.Other = other

    def __eq__(self, other):
        return isinstance(self, other)


class Dog(Animals):
    def __str__(self):
        return 'Dog'


class Cat(Animals):
    def __str__(self):
        return 'Cat'


class Bird(Animals):
    def __str__(self):
        return 'Bird'


class Other(Animals):
    def __init__(self, name: str):
        self.name = name

    def __str__(self):
        return f'Other(name: {self.name})'

Animals.__assign_enum_types__(Animals, Dog, Cat, Bird, Other)

del(Dog)
del(Cat)
del(Bird)
del(Other)

You do not have to understand the purpose of this code, just that, under the hood, an enum is represented as a number of classes.

You can compare these against the enum to determine their type.

# Continued from first example...

animal_1 = Animals.Cat
animal_2 = Animals.Other("Lion")

assert animal_1 == Animals.Cat
assert animal_2 == Animals.Other

assert animal_1 != animal_2

print(animal_2.name)

Most of this behavior is fairly normal. The most important part to note is that the value of a generic enum is ignored. This mean any Animal.Other will be equal to any other Animal.Other

Properties on generic enums are accessed via enum.property_name. So in this example, the property is accessed via animal_2.name.

A copy of this example code is available on GitHub.