python enums with attributes

Python 3.4 has a new Enum data type (which has been backported as enum34 and enhanced as aenum1). Both enum34 and aenum2 easily support your use case:

  • aenum (Python 2/3)

      import aenum
      class EnumWithAttrs(aenum.AutoNumberEnum):
          _init_ = 'a b'
          GREEN = 'a', 'b'
          BLUE = 'c', 'd'
    
  • enum34 (Python 2/3) or standard library enum (Python 3.4+)

      import enum
      class EnumWithAttrs(enum.Enum):
    
          def __new__(cls, *args, **kwds):
              value = len(cls.__members__) + 1
              obj = object.__new__(cls)
              obj._value_ = value
              return obj
          def __init__(self, a, b):
              self.a = a
              self.b = b
    
          GREEN = 'a', 'b'
          BLUE = 'c', 'd'
    

And in use:

>>> EnumWithAttrs.BLUE
<EnumWithAttrs.BLUE: 1>

>>> EnumWithAttrs.BLUE.a
'c'

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

2aenum also supports NamedConstants and metaclass-based NamedTuples.


For Python 3:

class Status(Enum):
    READY = "ready", "I'm ready to do whatever is needed"
    ERROR = "error", "Something went wrong here"

    def __new__(cls, *args, **kwds):
        obj = object.__new__(cls)
        obj._value_ = args[0]
        return obj

    # ignore the first param since it's already set by __new__
    def __init__(self, _: str, description: str = None):
        self._description_ = description

    def __str__(self):
        return self.value

    # this makes sure that the description is read-only
    @property
    def description(self):
        return self._description_

And you can use it as a standard enum or factory by type:

print(Status.READY)
# ready
print(Status.READY.description)
# I'm ready to do whatever is needed
print(Status("ready")) # this does not create a new object
# ready

Tags:

Python

Enums