On Wed, 27 Jul 2022 at 09:28, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote: > > On Tue, 26 Jul 2022 16:38:38 +0200, Cecil Westerhof <ce...@decebal.nl> > declaimed the following: > > >I need to get a random integer. At first I tried it with: > > from secrets import randbelow > > index = randbelow(len(to_try)) > > > >This works perfectly, but it took some time. So I thought I try: > > from random import SystemRandom > > index = SystemRandom().randint(0, len(to_try) - 1) > > > >A first indication is that the second version would take about two > >times as much time as the first. Is there a reason for this, or should > >this not be happening? > > Well, off the top of my head... > > For one generation of "index" you are first creating an instance of > SystemRandom(), using it to generate your random integer, and then > disposing of the instance. > > If you only need ONE random integer, the time difference probably > doesn't matter. OTOH, if you need many during the run, using > > sr = SystemRandom() > #stuff in some loop that generates multiple ints > index = sr.randint(...) > > Hmmm, wonder if there is a speed difference between > .randint(0, len(to_try) - 1) > and > .randint(1, len(to_try)) - 1 >
Probably not significant, since the same amount of arithmetic gets done either way. But switching to single-arg randrange(len(to_try)) will definitely help, and IMO is clearer as well (since the implication is selecting one from a group of items). Incidentally - if you are actually trying to select a specific item, you may want to consider random.choice. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
