Re: those darn exceptions

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From	Ben Finney <ben+python@benfinney.id.au>
Newsgroups	comp.lang.python
Subject	Re: those darn exceptions
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Chris Torek <nospam@torek.net> writes:

> But again, this is why I would like to have the ability to use some
> sort of automated tool, where one can point at any given line of
> code and ask: "what exceptions do you, my faithful tool, believe
> can be raised as a consequence of this line of code?"

“Why, any exception at all”.

> If you point it at the call to main():
>
>     if __name__ == '__main__':
>         main()
>
> then you are likely to get a useless answer ("why, any exception
> at all"); but if you point it at a call to os.read(), then you get
> one that is useful -- and tells you (or me) about the OverflowError.

No. The answer is *still* “why, any exception at all”. The name
‘os.read’ could be re-bound at run-time to any object at all, so a code
checker that you “point at any given line of code” can't know what the
name will be bound to when that line gets executed.

> If you point it at a call to len(x), then the tool tells you what
> it knows about type(x) and x.__len__.

Which information, before the code is executed, isn't determined.

-- 
 \           “The cost of education is trivial compared to the cost of |
  `\                                     ignorance.” —Thomas Jefferson |
_o__)                                                                  |
Ben Finney

Thread

those darn exceptions Chris Torek <nospam@torek.net> - 2011-06-21 01:43 +0000
  Re: those darn exceptions Chris Angelico <rosuav@gmail.com> - 2011-06-21 13:19 +1000
    Re: those darn exceptions Chris Torek <nospam@torek.net> - 2011-06-21 04:40 +0000
  Re: those darn exceptions Ben Finney <ben+python@benfinney.id.au> - 2011-06-21 14:04 +1000
  Re: those darn exceptions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-06-21 09:49 +0000
    Re: those darn exceptions Chris Torek <nospam@torek.net> - 2011-06-21 21:51 +0000
      Re: those darn exceptions John Nagle <nagle@animats.com> - 2011-06-27 11:52 -0700
  Re: those darn exceptions Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-06-23 20:16 +1200
    Re: those darn exceptions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-06-23 18:40 +1000
    Re: those darn exceptions Chris Torek <nospam@torek.net> - 2011-06-23 18:33 +0000
      Re: those darn exceptions Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-06-24 19:50 +1200
        Re: those darn exceptions Chris Torek <nospam@torek.net> - 2011-06-24 18:21 +0000
          Re: those darn exceptions Ben Finney <ben+python@benfinney.id.au> - 2011-06-25 10:25 +1000
            Re: those darn exceptions Chris Angelico <rosuav@gmail.com> - 2011-06-25 13:55 +1000
              Re: those darn exceptions steve+comp.lang.python@pearwood.info - 2011-06-26 00:28 +1000
                Re: those darn exceptions Chris Angelico <rosuav@gmail.com> - 2011-06-26 01:52 +1000

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