What are the caveats of inheriting from both str and Enum

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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

multiple-inheritance enums python-3.x python
2 Answers

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

user_2088800

This approach would work when the Enum Constants are always String. If you are expecting the right hand to be always a string value of the constant, this works.

Here is one example, this would not work if I want the rightHandside to be encoded as an integer 

   class Status(str, Enum):
       DEFAULT=1

   type(json.dumps(Status.DEFAULT)

would output as

user_28134830
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