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Re: Raise X or Raise X()?

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On 3/12/12 10:37 AM, Jean-Michel Pichavant wrote:
> 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"
>
> I prefer the raise X() version, it fulfils the zen of python :
>
> "Special cases aren't special enough to break the rules.
> There should be one-- and preferably only one --obvious way to do it."
>
> I still wonder why they've added the class raise form, on which purpose.

The class raise form used to be the only way to raise exceptions. To pass an 
argument, there was special syntax:

   raise Exception, "some message"

This syntax has been done away with in Python 3 in favor of regular calling 
conventions. Python 3 still allows bare classes, though. I also prefer to always 
raise instances of exceptions rather than bare exception classes. It simplifies 
the mental model.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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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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