Simple python enumeration class

enum.py

from collections import namedtuple


class Enum(tuple):
    def __new__(cls, *sequential, **named):
        new_cls = namedtuple(cls.__name__, sequential + tuple(named.keys()))
        return new_cls._make(range(len(sequential))+named.values())


class ChoicedEnum(tuple):
    def __new__(cls, *sequential, **named):
        new_cls = namedtuple(cls.__name__, sequential + tuple(named.keys()))
        new_cls.__items = range(len(sequential))+named.values()
        def iter(self):
            for item in self.__items:
                yield item
        new_cls.__iter__ = iter
        instance = new_cls._make(range(len(sequential)) + 
            [type(val) is tuple and val[1] or val for val in named.values()])
        return instance


e = Enum('ZERO', 'ONE', THREE=3, FOUR=4)
print e, e.ZERO, e.FOUR, tuple(e)

sizes = ChoicedEnum(SMALL = ('s', 'Small size'), BIG = ('b', 'Big size'))
print sizes.SMALL, tuple(sizes)