Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.python
Subject: Re: What behavior would you expect?
Date: Thu, 19 Feb 2015 22:18:10 -0800
Organization: A noiseless patient Spider
Lines: 16
Message-ID: <87r3tlds2l.fsf@jester.gateway.pace.com>
References: <mailman.18856.1424321059.18130.python-list@python.org> <mc4r7v$cm7$2@dont-email.me> <mailman.18884.1424358984.18130.python-list@python.org> <mc5fiq$a3f$3@dont-email.me> <mailman.18902.1424376675.18130.python-list@python.org> <mc6emp$j1q$1@dont-email.me> <mailman.18908.1424409419.18130.python-list@python.org> <mc6hd4$j1q$2@dont-email.me>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: mx02.eternal-september.org; posting-host="c694756f1077760bb5296aae16c74092"; logging-data="1733"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/9hfNFpIEthCNBXUvRNOhh"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)
Cancel-Lock: sha1:+LR/bRvtnQLQ9csEqM/3Wq4RVmM= sha1:BEnw6ZmftlHRH1zIA/Fu4cURwtA=
Xref: csiph.com comp.lang.python:85953

Dan Sommers <dan@tombstonezero.net> writes:
> I'd still prefer an exception to None, and we agree on that an empty
> string is bad because it's not a non-string and it could be too easily
> mistaken for a filename.

Empty string would be bad.  Sometimes I like to simulate an option type,
by returning the value as a 1-element list if there's a value, otherwise
as an empty list.  So you could say

  filename = get_filename(...)[0]

if you want an exception in the failure case, or you could do something
like

  fs = get_filename(...)
  if len(fs) == 0:  ... # didn't get a filename