On Apr 13, 2013, at 08:33 AM, Guido van Rossum wrote:
>(And yes, I am now +1 on documenting this mechanism.)
Here's what I've added to the flufl.enum documentation:
Customization protocol
======================
You can define your own enumeration value types by using the
``__value_factory__`` protocol. This is how the ``IntEnum`` type is
defined. As an example, let's say you want to define a new type of
enumeration where the values were subclasses of ``str``. First, define your
enumeration value subclass.
>>> from flufl.enum import EnumValue
>>> class StrEnumValue(str, EnumValue):
... def __new__(cls, enum, value, attr):
... return super(StrEnumValue, cls).__new__(cls, value)
And then define your enumeration class. You must set the class attribute
``__value_factory__`` to the class of the values you want to create.
>>> class StrEnum(Enum):
... __value_factory__ = StrEnumValue
Now, when you define your enumerations, the values will be ``str`` subclasses.
::
>>> class Noises(StrEnum):
... dog = 'bark'
... cat = 'meow'
... cow = 'moo'
>>> isinstance(Noises.cow, str)
True
-Barry
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