Calculate Python Enum each time when evaluated with datetime?

Question

Is there a way to create an Enum in Python that calculates the value each time the Enum attribute is accessed? Specifically, I'm trying to create an Enum class that stores values like TODAY, TOMORROW, etc. for a web app (in Django) that runs for many days and I want the value recalculated each time it's accessed in case the day changes. So, say, the app is launched on March 1, if the app makes the check for TODAY on March 3, it will return March 3 and not March 1 which is what it would be initialized for.

from enum import Enum
import datetime

class MyEnum(Enum):
    TODAY = datetime.datetime.now()
    TOMORROW = datetime.datetime.now() + datetime.timedelta(days=1)

Answer 1

You can do this by programming a descriptor, like:

from datetime import datetime, timedelta
from enum import Enum


class DtDiff:
    def __init__(self, delta=timedelta()):
        self.delta = delta

    def __get__(self, obj, objtype=None):
        return datetime.now() + self.delta


class MyEnum(Enum):
    TODAY = DtDiff()
    TOMORROW = DtDiff(timedelta(days=1))

But in this case this will even nullify most functionalities of the Enum, hence it is likely not a good idea.

Probably a better way is just define a function on the Enum, like:

from datetime import datetime, timedelta
from enum import Enum


class MyEnum(Enum):
    TODAY = timedelta(0)
    TOMORROW = timedelta(days=1)

    @property
    def timestamp(self):
        return datetime.now() + self.value

You then can just get the timestamp with:

>>> MyEnum.TODAY.timestamp
datetime.datetime(2023, 6, 24, 19, 32, 41, 854253)

which looks like a minimal amount of work to get the timestamp for an enum choice.