Is there a way to return a custom value for min and max in Python?

I have a custom class,

class A:
    def __init__(self, a, b):
        self.a = a
        self.b = b

The class is not iterable or indexable or anything like that. If at all possible, I would like to keep it that way. Is it possible to have something like the following work?

>>> x = A(1, 2)
>>> min(x)
1
>>> max(x)
2

What got me thinking about this is that min and max are listed as "Common Sequence Operations" in the docs. Since range is considered to be a sequence type by the very same docs, I was thinking that there must be some sort of optimization that is possible for range, and that perhaps I could take advantage of it.

Perhaps there is a magic method that I am not aware of that would enable this?

Answer

Yes. When min takes one arguments it assumes it to be an iterable, iterates over it and takes the minimum value. So,

class A:
    def __init__(self, a, b):
        self.a = a
        self.b = b
    def __iter__(self):
        yield self.a
        yield self.b

Should work.

Additional Note: If you don't want to use __iter__, I don't know of way to do that. You probably want to create your own min function, that calls some __min__ method if there is one in the argument it is passed to and calls the old min else.

oldmin = min
def min(*args):
    if len(args) == 1 and hasattr(args[0], '__min__'):
        return args[0].__min__()

    else:
        return oldmin(*args)