[Tutor] Handling missing positional arguments

[Kent Johnson]

On Thu, Nov 19, 2009 at 5:47 PM, Geoff Dutton <geoff.dutton at noaa.gov> wrote:
> Do you have recommendations for handling missing positional arguments?  I'm
> a huge fan of OptionParser module and use it in several programs to handle
> options, but there must be an eligant way of handling missing arguments and
> alerting the user.  Here is how I have done it ...
>
> import sys
> from subprocess import call
> from optparse import OptionParser
>
> if __name__=='__main__':
>
>     opt = OptionParser(
>         usage = "usage: %prog [options] site year",
>         description = "Count number of ITX files from a station for a given
> year."
>     )
>     opt.add_option("-e", action="store",
>             dest="email_add", help="send table as email")
>     opt.add_option("-l", '--lenght', action="store", default="30",
>             dest="len", help="Number of lines in table.")
>
>     (options, args) = opt.parse_args()
>
>     if len(args) != 2:
>         call(["countinj.py", "-h"])
>         sys.exit()

opt.print_help() seems to be what you want here.

Kent

>
>     (site, year) = args
>
>     <snip>
>
>
> I like the "help" that OptionParser creates for my program when called with
> the -h or --help option. Thus when len(args) is not correct I call the
> program using the call function in the module subprocess.  But.... Do I
> really need go to this trouble?  Is there a better way?
>
> Thanks,
> Geoff
>
> --
> NOAA Earth System Research Laboratory
> Global Monitoring Division
> 325 Broadway, R/GMD1
> Boulder, CO 80305
>
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