On Sat, 7 Apr 2012 05:23:25 -0700 (PDT) andrew cooke <and...@acooke.org> wrote:
> > hi, > > please, what am i doing wrong here? the docs say > http://docs.python.org/release/3.1.3/library/stdtypes.html#comparisons "in > general, __lt__() and __eq__() are sufficient, if you want the conventional > meanings of the comparison operators" but i am seeing > > > assert 2 < three > E TypeError: unorderable types: int() < IntVar() > > with this test: > > > class IntVar(object): > > def __init__(self, value=None): > if value is not None: value = int(value) > self.value = value > > def setter(self): > def wrapper(stream_in, thunk): > self.value = thunk() > return self.value > return wrapper > > def __int__(self): > return self.value > > def __lt__(self, other): > return self.value < other > > def __eq__(self, other): > return self.value == other > > def __hash__(self): > return hash(self.value) > > > class DynamicTest(TestCase): > > def test_lt(self): > three = IntVar(3) > assert three < 4 > assert 2 < three > assert 3 == three > > so what am i missing? > I think that quote from the docs is just to point out that you only need those two (== and <) to derive any of the other comparisons; but not to imply that a class that only defines those two will automatically possess the others. However, you can do that, with functools.total_ordering. Regards, John -- http://mail.python.org/mailman/listinfo/python-list
