Python style: exceptions vs. sys.exit()

Grant Edwards invalid at invalid
Wed Sep 24 16:09:31 CEST 2008

On 2008-09-24, Steven D'Aprano <steven at> wrote:
> On Tue, 23 Sep 2008 13:25:26 -0700, Drake wrote:
>> I have a general question of Python style, or perhaps just good
>> programming practice.
>> My group is developing a medium-sized library of general-purpose Python
>> functions, some of which do I/O. Therefore it is possible for many of
>> the library functions to raise IOError Exceptions. The question is:
>> should the library function be able to just dump to sys.exit() with a
>> message about the error (like "couldn't open this file"), or should the
>> exception propagate to the calling program which handles the issue?
>> Thanks in advance for anyone who can either answer my question or point
>> me to where this question has already been answered.
> Presumably somebody has suggested that calling sys.exit() was a good 
> option. I'm curious to what possible reason they could give for such a 
> poor choice.

Same here.  It's like an automotive engine controls designer
asking if a failed O2 sensor should turn on the check engine
light or blow up the car.

Grant Edwards                   grante             Yow! Mr and Mrs PED, can I
                                  at               borrow 26.7% of the RAYON
                                 TEXTILE production of the
                                                   INDONESIAN archipelago?

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