Python 允许在枚举中使用一组特定的未定义值

这是可能的，但需要使用Python3.9或更高版本，并且确实使用了一种当前未记录在案的数据 struct (_value2member_map_):

from enum import IntEnum

class RangedEnum(IntEnum):

    def __repr__(self):
        if self._name_:
            return f"<{self.__class__.__name__}.{self._name_}: {self._value_}>"
        else:
            return f"<{self.__class__.__name__}: {self._value_}>"

    def __init_subclass__(cls, valid_range):
        cls.valid_range = valid_range

    @classmethod
    def _missing_(cls, value):
        start, stop = cls.valid_range
        if start <= value <= stop:
            member = int.__new__(cls, value)
            member._name_ = None
            member._value_ = value
            cls._value2member_map_[value] = member
            return member


class Result(RangedEnum, valid_range=(4, 10)):
    A = 0
    B = 1
    C = 3

和一些轻量级测试代码:

>>> for v in (0, 1, 2, 3, 4, 5, 9, 10, 11):
...     try:
...         Result(v)
...     except ValueError:
...         print('nope on', v)
... 
<Result.A: 0>
<Result.B: 1>
nope on 2
<Result.C: 3>
<Result: 4>
<Result: 5>
<Result: 9>
<Result: 10>
nope on 11

¹透露:我是Python stdlib Enum、enum34 backport和Advanced Enumeration (aenum)库的作者.