二、Enum 的源码

class Enum(metaclass=EnumMeta):
    """Generic enumeration.
    Derive from this class to define new enumerations.
    """

class EnumMeta(type):
    """Metaclass for Enum"""
    @property
    def __members__(cls):
        """Returns a mapping of member name->value.
        This mapping lists all enum members, including aliases. Note that this
        is a read-only view of the internal mapping.
        """
        return MappingProxyType(cls._member_map_)