Request for package: micropython-enum

[desowin]

I would like micropython to have support for IntEnum class. Base Enum would be nice to have, although just bare IntEnum would be enough in my opinion.

[stlehmann]

Enums are especially useful when it comes to static type-checking. So it would be great if the implementation of this enum type allowed type-checking via mypy. This means all values need to be an instance of the defined enum-type.

>>> class MyEnum(enum.IntEnum):
...    A = 1
...    B = 2

>>> isinstance(MyEnum.A, MyEnum)
True

[njourdane]

I'm also interested by enum in MicroPython.

In the meantime, I found here this workaround:

def enum(**enums: int):
    return type('Enum', (), enums)

Number = enum(ONE=1, TWO=2, THREE=3)

numbers = (Number.ONE, Number.TWO)

[matejcik]

for type-checking, I'm using the following trick:

if TYPE_CHECKING:
    from enum import IntEnum
else:
    IntEnum = object

class Fruit(IntEnum):
    APPLE = 1
    PEAR = 2

def print_fruit(fruit: Fruit):
    if fruit == Fruit.APPLE:
         print("apple")

print_fruit(Fruit.APPLE)

[brotherdust]

This workaround is excellent! I combined it with const for my purposes:

OP_RW = enum(
        READ = const(0b1),
        WRITE = const(0b1)
    )

[esologic]

+1 for a real implementation of this

[i33l]

class State(int):
    pass

State.OFF = State(0)
State.ON = State(1)

But when have been imported getting "Unresolved attribute reference" warning.

[andrewleech]

+1 for a real implementation of this

The cpython implementation is surprisingly very complicated and relies heavily on metaclasses which aren't supported in micropython:

https://github.com/python/cpython/blob/f585ed19ad00f78ed99ba44be5e333c056076160/Lib/enum.py#L1051

As such any micropython implementation will need to be completely custom really, at which point we need to clearly define which aspects of Enum we want to support first, before figuring out how to implement them!

[andrewleech]

class State(int):
    pass

State.OFF = State(0)
State.ON = State(1)

But when have been imported getting "Unresolved attribute reference" warning.

There are a number of limitations when subclassing builtins in micropython, especially int because behind the scenes it's particularly optimised. Eg. https://docs.micropython.org/en/latest/genrst/builtin_types.html#no-int-conversion-for-int-derived-types-available

[bredbord]

+1 for an implementation of this as well.

[IhorNehrutsa]

docs/library/enum.rst: Add Enum class. #16842

[IhorNehrutsa]

Implementation in:
micropython-lib/python-stdlib/enum/enum.py: Add Enum class. #980