Comparable classes in Python 3

Question

What is the standard way of making a class comparable in Python 3? (For example, by id.)

Answer 1

You said you are trying to do this:

max((f(obj), obj) for obj in obj_list)[1]

You should simply do this:

max(f(obj) for obj in obj_list)

EDIT: Or as gnibbler said: max(obj_list, key=f)

But you told gnibbler you need an object reference to the max object. I think this is simplest:

def max_obj(obj_list, max_fn):
    if not obj_list:
        return None

    obj_max = obj_list[0]
    f_max = max_fn(obj)

    for obj in obj_list[1:]:
        if max_fn(obj) > f_max:
            obj_max = obj
    return obj_max

obj = max_obj(obj_list)

Of course you might want to let it raise an exception rather than return none if you try to find the max_obj() of an empty list.