> exception[s] can be relatively slow

That really depends on your hit rate. Say you have a generator returning objects and you don't know if they have an attribute. You can use hasattr(..) to check or just try to use the attribute and catch the AttributeError.

One-on-one the exception is slower, but there comes a point where the exception is rare enough that actively checking every single item is slower. Eg if only 1-in-1000 doesn't have the attribute, just mop up with an exception.