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Re: LBYL vs EAFP

References <5110415c$0$29986$c3e8da3$5496439d@news.astraweb.com>
Date 2013-02-05 10:38 +1100
Subject Re: LBYL vs EAFP
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.1338.1360021130.2939.python-list@python.org> (permalink)

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On Tue, Feb 5, 2013 at 10:16 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> A third option is not to check x at all, and hope that it will blow up at
> some arbitrary place in the middle of my code rather than silently do the
> wrong thing. I don't like this idea because, even if it fails, it is better
> to fail earlier than later.
>
> Comments, thoughts and opinions please.

It depends on what could cause the failure. If only a programming
error could cause x to not be a number, I'd go with your third option
- let it blow up anywhere, and follow the trace. That option requires
zero forethought, which translates directly into programmer
efficiency. But if x came from a user,  then I'd be checking inputs at
a much earlier point.

Those are the two obvious cases though, and I'm assuming your
situation is neither of them. Writing library code is half way in
between. With the specific examples given, I wouldn't like to use "x +
0" as a check; it seems dodgy. Firstly because it doesn't look like a
data type check (though a comment can help with that), and secondly
because something might very well support having a number added to it
while definitely not itself being a number - eg something along the
lines of a database cursor. So I would recommend LBYL for this
particular case.

ChrisA

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Thread

LBYL vs EAFP Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-05 10:16 +1100
  Re: LBYL vs EAFP Chris Angelico <rosuav@gmail.com> - 2013-02-05 10:38 +1100
    Re: LBYL vs EAFP Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-05 03:52 +0000
      Re: LBYL vs EAFP Chris Angelico <rosuav@gmail.com> - 2013-02-05 16:19 +1100
  Re: LBYL vs EAFP Ian Kelly <ian.g.kelly@gmail.com> - 2013-02-04 16:46 -0700
    Re: LBYL vs EAFP Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-05 04:52 +0000
      Re: LBYL vs EAFP Chris Angelico <rosuav@gmail.com> - 2013-02-05 16:20 +1100
        Re: LBYL vs EAFP Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-05 06:31 +0000
          Re: LBYL vs EAFP Pete Forman <petef4+usenet@gmail.com> - 2013-02-05 09:49 +0000
            Re: LBYL vs EAFP Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-05 23:04 +1100
              Re: LBYL vs EAFP Chris Angelico <rosuav@gmail.com> - 2013-02-05 23:25 +1100
      Re: LBYL vs EAFP Ian Kelly <ian.g.kelly@gmail.com> - 2013-02-04 22:40 -0700
  Re: LBYL vs EAFP Dave Angel <davea@davea.name> - 2013-02-04 18:55 -0500
  Re: LBYL vs EAFP Chris Angelico <rosuav@gmail.com> - 2013-02-05 11:45 +1100
  Re: LBYL vs EAFP Ethan Furman <ethan@stoneleaf.us> - 2013-02-04 16:26 -0800
  Re: LBYL vs EAFP Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-02-05 01:00 +0000
  Re: LBYL vs EAFP Terry Reedy <tjreedy@udel.edu> - 2013-02-05 02:53 -0500

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