What are the caveats of inheriting from both str and Enum

Question

What are the caveats (if any) of using a class that inherits from both str and Enum?

This was listed as a possible way to solve the problem of Serialising an Enum member to JSON

from enum import Enum

class LogLevel(str, Enum):
    DEBUG = 'DEBUG'
    INFO = 'INFO'

Of course the point is to use this class as an enum, with all its advantages

score 9 · Accepted Answer · edited Mar 17 '20 at 23:39

9

When inheriting from str, or any other type, the resulting enum members are also that type. This means:

they have all the methods of that type
they can be used as that type
and, most importantly, they will compare with other instances of that type

That last point is the most important: because LogLevel.DEBUG is a str it will compare with other strings -- which is good -- but will also compare with other str-based Enums -- which could be bad.

Info regarding subclassing enum from the documentation

edited Mar 17 '20 at 23:39

Alonme

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answered Mar 17 '20 at 19:09

Ethan Furman

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If the comparison is done as if they were strings there i guess that there will also be a slow down? – Alonme Mar 17 '20 at 20:48
@Alonme: Not enough to worry about. – Ethan Furman Mar 17 '20 at 23:40

What are the caveats of inheriting from both str and Enum

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