How to define new for Enum subclasses?

Question

I have a case where I have digit-only code values and some associated standard text. I have a number of fixed code sets I would like to define as enumerations where I can reuse the __new__ method that attaches the associated text to the members (I am using json to dump these, so want the serialization to reflect the value and not the text), but I am unable to get it work.

Here is my attempt:

import enum class Code(str): def __new__(cls, code: str) -> None: if not code.isdigit(): raise ValueError("code must be digits") return str.__new__(cls, code) class CodeEnum(Code, enum.Enum): def __new__(cls, code: str, text: str) -> None: obj = Code.__new__(cls, code) obj._value_ = str(obj) obj.text = text return obj class CodeSet1(CodeEnum): CODE_0001 = "0001", "Code 0001"

However, I get an AttributeError:

AttributeError: 'CodeSet1' object has no attribute '_name_'. Did you mean: 'name'?

Is there a way to resolve this such that I can reuse the __new__ method in CodeEnum for each of my code sets?

Ethan Furman · Accepted Answer · 2022-11-05 04:35:58Z

The proper definition for CodeEnum is:

class CodeEnum(Code, enum.Enum): def __new__(cls, code: str, text: str) -> None: obj = super().__new__(cls, code) obj._value_ = Code(code) obj.text = text return obj

The major difference is using super(). _value_ is a Code instead of just a str because it should be the same core type as the enum itself.

Disclosure: I am the author of the Python stdlib Enum, the enum34 backport, and the Advanced Enumeration (aenum) library.

Collectives™ on Stack Overflow

How to define new for Enum subclasses?

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related