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Re: Raise X or Raise X()?

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On Sun, Mar 11, 2012 at 1:37 PM, Irmen de Jong <irmen.NOSPAM@xs4all.nl> wrote:
> On 11-3-2012 20:04, bvdp wrote:
>> Which is preferred in a raise: X or X()? I've seen both. In my specific case I'm dumping out of a deep loop:
>>
>> try:
>>   for ...
>>     for ...
>>       for ...
>>         if match:
>>            raise StopInteration()
>>          else ...
>>
>> except StopInteration:
>>    print "found it"
>
> "raise X" is a special case of the 3-args raise. Effectively it just raises an instance
> of X which is constructed with an empty argument list. Therefore, "raise X()" is
> equivalent, as far as I know.
>
> See http://docs.python.org/reference/simple_stmts.html#the-raise-statement

Note that the 3-argument form of `raise` has been eliminated in Python 3.
However, both:
    raise an_exception_instance
and:
    raise AnExceptionClass # will have a blank error message
are still permitted.

Interesting stylistic question though. I'd support the X() form for
uniformity with the majority of cases where an error message is
specified for the exception.

Cheers,
Chris

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Thread

Raise X or Raise X()? bvdp <bob@mellowood.ca> - 2012-03-11 12:04 -0700
  Re: Raise X or Raise X()? Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2012-03-11 21:37 +0100
    Re: Raise X or Raise X()? Chris Rebert <clp2@rebertia.com> - 2012-03-11 14:49 -0700
    Re: Raise X or Raise X()? Stefan Behnel <stefan_ml@behnel.de> - 2012-03-12 14:52 +0100
      Re: Raise X or Raise X()? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-03-12 15:08 +0000
        Re: Raise X or Raise X()? Stefan Behnel <stefan_ml@behnel.de> - 2012-03-12 17:08 +0100
  Re: Raise X or Raise X()? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-03-11 23:59 +0000
    Re: Raise X or Raise X()? bvdp <bob@mellowood.ca> - 2012-03-11 18:53 -0700
    Re: Raise X or Raise X()? MRAB <python@mrabarnett.plus.com> - 2012-03-12 02:26 +0000
  Re: Raise X or Raise X()? Jean-Michel Pichavant <jeanmichel@sequans.com> - 2012-03-12 11:37 +0100
  Re: Raise X or Raise X()? Robert Kern <robert.kern@gmail.com> - 2012-03-12 12:47 +0000
  Re: Raise X or Raise X()? James Elford <fil.oracle@gmail.com> - 2012-03-12 13:06 +0000
  Re: Raise X or Raise X()? Chris Angelico <rosuav@gmail.com> - 2012-03-13 00:13 +1100

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