On Sun, 4 Oct 2009 04:46:19 am Yuvgoog Greenle wrote:
> I just think that if a parser error is causing the SystemExit, I
> would rather catch a parser error than catching a SystemExit for the
> sake of readability. It saves me the comments:
>
> # Catching SystemExit because parse_args() throws SystemExit on
> parser errors.
But why are you catching the error? As a general rule, you *want* your
command line app to exit if it can't understand the arguments you pass
to it. What else can it do? Guess what you wanted?
Assuming you have a reason for catching the exception, I don't see that
there's any difference in readability between these:
parser = argparse.ArgumentParser()
setup_args(parser)
try:
ns = parser.parse_args()
except argparse.ParserError:
process_error()
else:
main(ns)
and:
parser = argparse.ArgumentParser()
setup_args(parser)
try:
ns = parser.parse_args()
except SystemExit:
process_error()
else:
main(ns)
You don't need a comment warning that you are catching SystemExit
because parse_args raises SystemExit, any more than you need a comment
saying that you are catching ValueError because some function raises
ValueError. The fact that you are catching an exception implies that
the function might raise that exception. A comment like:
"Catching SystemExit because parse_args() throws SystemExit on parser
errors."
is up them with comments like this:
x += 1 # Add 1 to x.
--
Steven D'Aprano
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