Ring datatype for Python

ring.py

def _adj_index(method):
    def _dec(instance, *args):
        if isinstance(args[0], int):
            index = args[0] % len(instance)
            return method(instance, index, *args[1:])
        return method(instance, args)
    return _dec


class Ring(list):
    """
    Ring datatype.
    """

    def __iter__(self):
        while True:
            for i in xrange(len(self)):
                yield self[i]

    def __getitem__(self, item):
        if isinstance(item, tuple):
            slice = item[0]
            return Ring([
                self[i]
                for i in xrange(slice.start, slice.stop, slice.step)])
        return super(Ring, self).__getitem__(item)

    __getitem__ = _adj_index(__getitem__)
    __setitem__ = _adj_index(list.__setitem__)
    __delitem__ = _adj_index(list.__delitem__)

    def __getslice__(self, i, j):
        return Ring([
            self[x]
            for x in range(i, j)])