Python dynamic enum

Question

I would like to create dynamic enums in python loaded from a SQL Table. The output of SQL will be a list of tuplets, which with I want to fill the attributes of the enum.

Lets say I receive this list:

lst = [('PROCESS_0', 0, "value", 123, False), ('PROCESS_1',1,"anothervalue", 456, True)]

I now want to fill the values in the enum below:

class Jobs(IntEnum):
    def __new__(cls, value: int, label: str, heartbeat: int = 60, heartbeat_required: bool = False):
        obj = int.__new__(cls, value)
        obj._value_ = value
        obj.label = label
        obj.heartbeat = heartbeat
        obj.heartbeat_required = heartbeat_required
        return obj

The first variable in the tuple should be the variable name of the enum, I have solved this with:

locals()['Test'] = (0, '', 789, False)

But this only works for single values, it seems that I can not run a for loop within enum. When using a for loop like this:

 for i in lst:
    locals()[i[0]] = (i[1], i[2], i[3])

Python sends this error TypeError: Attempted to reuse key: 'i' which propably comes from enums only having constants.

Is there any (possibly elegant) solution for this?

Many thanks in advance!

I am running code example 3 and 4 within the Enum class. My current python version is 3.8.5. — max
– max, Commented Jun 7, 2022 at 10:25
If I understand your use case, I would go for a dict of namedtuples (or even dataclasses if you want to be able to change the values of the attributes) — gimix
– gimix, Commented Jun 7, 2022 at 10:25

Ethan Furman · Accepted Answer · 2022-06-07 17:55:43Z

1

You need to use _ignore_ = "i". Something like:

class Jobs(IntEnum):

    _ignore_ = "i"

    def __new__(cls, value, label, heartbeat=60, heartbeat_required=False):
        obj = int.__new__(cls, value)
        obj._value_ = value
        obj.label = label
        obj.heartbeat = heartbeat
        obj.heartbeat_required = heartbeat_required
        return obj

    for i in lst:
        locals()[i[0]] = i[1:]

answered Jun 7, 2022 at 17:55

Ethan Furman

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Yang Bo · Accepted Answer · 2023-02-14 21:23:58Z

0

Check the example at https://docs.python.org/3/howto/enum.html#timeperiod

Note that the _ignore_ can be avoided in favor of dict comprehension

from datetime import timedelta
class Period(timedelta, Enum):
    "different lengths of time"
    vars().update({ f"day_{i}": i for i in range(367) })

Then you can access all possible enum values via Period.__members__

edited Feb 14, 2023 at 21:23

answered Feb 14, 2023 at 21:13

Yang Bo

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