On Sun, May 31, 2020 at 06:45:01AM +1000, Chris Angelico wrote:
> On Sun, May 31, 2020 at 6:14 AM Mike Miller <python-id...@mgmiller.net> wrote:
> >
> >
> > On 2020-05-28 18:02, Greg Ewing wrote:
> > >> If __name__ == '__main__':
> > >> sys.exit(main(sys.argv[1:]))
> > >
> > > It's not clear that exiting with the return value of main() is
> > > the most Pythonic thing to do -- it's more of a C idiom that
> >
> >
> > If you'd like a script to be uhh, highly-scriptable, returning one of the
> > os.EX_* status codes can be useful to communicate back to the calling shell
> > what
> > happened.
> >
> > First catch the exceptions, convert to the appropriate status code, then
> > return
> > at the end.
> >
>
> OR! You could just do nothing. And then, if SystemExit is raised,
Well, that's very fine and good, but the chances are remote that
SystemExit will be raised if I do nothing. More likely it will be some
other exception.
In order to raise SystemError, you need to catch the exception that
actually occurred, convert it to an os.EX_* error code, and at that
point it's entirely up to you whether you return from main() and let the
sys.exit() wrapper handle the exit, or call sys.exit directly.
Here's my preference: a function can have many returns, and that's
fine. But an application should only have one (or at most a few) exit
points, and they should never, ever be buried inside a function that
someone might want to call.
What's wrong with this test code? It's buggy. Can you see why?
unittest.main()
doctest.testmod(__main__)
> Python will return that exit code to the calling process (whether it's
> a shell or not). Python even provides a convenient function sys.exit
> for raising SystemExit with a specific code...
I'm not entirely sure, but I *think* that both "tritium-list" and Mike
may be aware of this, since they are calling sys.exit to do precisely
that *wink*
> Don't catch what you can't deal with.
That's good advice, but how does it apply here since Mike clearly can
deal with the exceptions. He even tells you what he does:
"First catch the exceptions, convert to the appropriate status code,
then return at the end."
Which seems like excellent advice to me.
--
Steven
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