Re: Re: optparse questions

Thanks all for your help.  I think I understand much better how to use 
the optparse module.  As I find more questions while writing the 
script, I know where to ask.
Thanks,
Jeremy

On Jun 6, 2004, at 12:35 PM, David Goodger wrote:

> Greg Ward wrote:
> [Jeremy Conlin (I presume)]
> >> I am creating a script that requires one argument (the input
> >> filename) and one optional argument (the output filename).
>
> [Greg Ward]
> > It sounds to me like you don't quite understand the difference
> > between arguments, options, and option arguments.
>
> While the Tao doc is useful, I don't think there's any problem with
> Jeremy's approach, syntax like this:
>
>     command [options] file1 [file2]
>
> That's options (optional by default), one required positional
> argument, and one optional positional argument.  We use similar syntax
> with Docutils:
>
>     rst2html.py [options] [<source> [<destination>]]
>
> If one positional argument is passed, it's the source.  If two, the
> first is the source and the second is the destination.  The defaults
> are STDIN for source and STDOUT for destination.  So "rst2html.py"
> (with no arguments) is the equivalent of "rst2html.py - -" using the
> standard meaning of "-".
>
> To code Jeremy's command (one required positional argument, one
> optional), use this:
>
>    parser = OptionParser(
>        usage="%prog [options] input_file [output_file]")
>    parser.add_option("-m", "--meshtal", action="store_true", dest='m',
>                      default=False,
>                      help='Input deck uses mesh tallies')
>    (options, args) = parser.parse_args()
>    if len(args) < 1 or len(args) > 2:
>        parser.error("wrong number of arguments: 1 or 2 required")
>    infile = open(args[0])
>    if len(args) == 2:
>        outfile = open(args[1], "w")
>    else:
>        outfile = sys.stdout
>    # check for -m option:
>    if options.m:
>        # do something
>        ...
>
> I'd drop the "dest='m'" though, and use the default of "meshtal".
> Makes the code more self-documenting.
>
> Definitely do read the updated docs.
>
> -- 
> David Goodger <http://python.net/~goodger>
>



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