Using NamedTuple with custom Enum

[SultanOrazbayev]

Documentation

This issue is related to #114071 and @ethanfurman suggested creating an isolated issue:

The handling of NamedTuple with a custom Enum is unexpected. Here are two examples that seek to achieve the same thing, but one will fail when using NamedTuple.

Using dataclasses (works):

from dataclasses import dataclass
from enum import Enum

@dataclass
class CodeLabel:
    code: int
    label: str

class LabelledEnumMixin:

    labels = {}

    def __new__(cls, codelabel: CodeLabel):
        member = object.__new__(cls)
        member._value_ = codelabel.code
        member.label = codelabel.label
        cls.labels[codelabel.code] = codelabel.label
        return member

    @classmethod
    def list_labels(cls):
        return list(l for c, l in cls.labels.items())



class Test(LabelledEnumMixin, Enum):
    A = CodeLabel(1, "Label A")
    B = CodeLabel(2, "Custom B")
    C = CodeLabel(3, "Custom label for value C + another string")

Test.list_labels()

Using NamedTuple (fails):

from typing import NamedTuple
from enum import Enum

class CodeLabel(NamedTuple):
    code: int
    label: str

class LabelledEnumMixin:

    labels = {}

    def __new__(cls, codelabel: CodeLabel):
        member = object.__new__(cls)
        member._value_ = codelabel.code
        member.label = codelabel.label
        cls.labels[codelabel.code] = codelabel.label
        return member

    @classmethod
    def list_labels(cls):
        return list(l for c, l in cls.labels.items())



class Test(LabelledEnumMixin, Enum):
    A = CodeLabel(1, "Label A")
    B = CodeLabel(2, "Custom B")
    C = CodeLabel(3, "Custom label for value C + another string")

Test.list_labels()

Linked PRs

• gh-114149: fix tuple subclass handling when using custom __new__ #114160
• [3.12] gh-114149: [Enum] fix tuple subclass handling when using custom __new__ (GH-114160) #114196
• [3.11] gh-114149: [Enum] fix tuple subclass handling when using custom __new__ (GH-114160) #114197
• gh-114149: [Enum] revert #114160 and add more tuple-subclass tests #114215
• [3.12] gh-114149: [Enum] revert GH-114196 and add more tuple-subclass tests (GH-114215) #114218