Trivial performance questions

[Peter Otten]

Brian Patterson wrote:

> I have noticed in the book of words that hasattr works by calling getattr
> and raising an exception if no such attribute exists.  If I need the value
> in any case, am I better off using getattr within a try statement myself,
> or is there some clever implementation enhancement which makes this a bad
> idea?

In rare cases, i. e. when attribute access has side effects, there are not
only differences in performance, but also in the result:

class AskMeOnce(object):
    def __getattribute__(self, name):
        result = object.__getattribute__(self, name)
        delattr(self, name)
        return result


t = AskMeOnce()
t.color = "into the blue"

#raises an exception
#if hasattr(t, "color"):
#    print t.color

#works
try:
    print t.color
except AttributeError:
    pass

:-)
Peter