On Tue, Oct 11, 2016 at 7:02 AM, Paul Moore <p.f.mo...@gmail.com> wrote: > Interesting idea. There may be some issues - consider an object that > may optionally have a handler method handle_event, and you want to > call that method if it exists: > > handler = getattr(obj, 'handle_event', None) > if handler: > # prepare arguments > handler(args)
This isn't a problem if you test for None: "if handler is not None". I was going to concede that there are probably other cases where that doesn't help, but can't think of any. In what case would a callable also evaluate to False, or you have a collection of arbitrary mixed values and you are testing their truthiness? So perhaps always using a None test is the correct answer if we add the warning. That said, I have no illusions that I know all possible use cases... :) > > That could would break (technically, it would produce an incorrect > warning) with this change. > > I do think that the scenario you described is a valid one - and > there's no obvious "better name". The stdlib module pathlib uses the > same pattern "my_path.is_absolute()", and IIRC I've made the mistake > you described (although I don't recall any major trauma, so the > problem was probably fixed relatively quickly). FWIW, I do the same thing from time to time and I usually only catch it when writing unit tests. I'm +1 to a warning as proposed. -eric _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
