How to get last Friday?

The code below should return last Friday, 16:00:00. But it returns Friday of previous week. How to fix that?

now = datetime.datetime.now()
test = (now - datetime.timedelta(days=now.weekday()) + timedelta(days=4, weeks=-1))
test = test.replace(hour=16,minute=0,second=0,microsecond=0)

Upd. I use the following approach now - is it the best one?

now = datetime.datetime.now()
if datetime.datetime.now().weekday() > 4:
    test = (now - datetime.timedelta(days=now.weekday()) + timedelta(days=4))
else:
    test = (now - datetime.timedelta(days=now.weekday()) + timedelta(days=4, weeks=-1))
test = test.replace(hour=16,minute=0,second=0,microsecond=0)

Upd2. Just to give an example. Let's assume that today is Oct 5, 2012. In case current time is equal to or less than 16:00 it should return Sep 28, 2012, otherwise - Oct 5, 2012.