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Date: Wed, 15 May 2013 09:08:12 -0500
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Subject: Re: Determine actually given command line arguments
From: Skip Montanaro <skip@pobox.com>
To: Henry Leyh <henry.leyh@ipp.mpg.de>
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Xref: csiph.com comp.lang.python:45343

> Yes, I was trying that and it sort of works with strings if I use somethi=
ng sufficiently improbable like "__UNSELECTED__" as default.  But it gets d=
ifficult with boolean or even number arguments where you just may not have =
valid "improbable" defaults.  You could now say, so what, it's the default =
anyway.  But in my program I would like to distinguish between given and no=
t given arguments rather than between default and non-default.

Initialize all your arg variables to None, then after command line
processing, any which remain as None weren't set on the command line.
At that point, set them to the actual defaults.  I think that's a
pretty common idiom.

Note: I am an old cranky dude and still use getopt.  This idiom is
pretty easy there.  YMMV with argparse or optparse.

Skip