String-based enum in Python

Question

To encapsulate a list of states I am using enum module:

from enum import Enum

class MyEnum(Enum):
    state1='state1'
    state2 = 'state2'

state = MyEnum.state1
MyEnum['state1'] == state  # here it works
'state1' == state  # here it does not throw but returns False (fail!)

However, the issue is that I need to seamlessly use the values as strings in many contexts in my script, like:

select_query1 = select(...).where(Process.status == str(MyEnum.state1))  # works but ugly

select_query2 = select(...).where(Process.status == MyEnum.state1)  # throws exeption

How to do it avoiding calling additional type conversion (str(state) above) or the underlying value (state.value)?

Answer 1

It seems that it is enough to inherit from str class at the same time as Enum:

class MyEnum(str, Enum):
    state1 = 'state1'
    state2 = 'state2'

The tricky part is that the order of classes in the inheritance chain is important as this:

class MyEnum(Enum, str):
    state1 = 'state1'
    state2 = 'state2'

throws:

TypeError: new enumerations should be created as `EnumName([mixin_type, ...] [data_type,] enum_type)`

With the correct class the following operations on MyEnum are fine:

print('This is the state value: ' + state)

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As a side note, it seems that the special inheritance trick is not needed for formatted strings which work even for Enum inheritance only:

msg = f'This is the state value: {state}'  # works without inheriting from str