argparse limitations

[Benoist Laurent]

Really sorry about that.

So, for the community, below is the full code for a tool that behaves like a Unix standard tool.
It takes in argument the files to process and a command.

"""Just to setup a command-line parser that acts just like a unix
standard tool."""

import argparse
import sys

def define_options():
    parser = argparse.ArgumentParser()
    parser.add_argument("fname", help="input file", nargs="*")

    # create subparsers
    subparsers = parser.add_subparsers(dest="cmd", metavar="command")

    # create the parser for the "foo" command
    get_parser = subparsers.add_parser("foo", help="foo help")
    get_parser.add_argument("-n", help="number of foo to print", 
                            type=int, default=10)

    # create the parser for the "bar" command
    sum_parser = subparsers.add_parser("bar", help="bar help")
    
    return parser


if __name__ == '__main__':
    args = define_options().parse_args()

    if not args.fname:
        content = sys.stdin.read()
        # do something
    else:
        for fname in args.fname:
            with(open(fname, "rt")) as f:
                content = f.read()
            # do somet


Benoist



Le Jul 31, 2012 à 11:55 AM, Oscar Benjamin a écrit :

> 
> On Jul 31, 2012 10:32 AM, "Benoist Laurent" <benoist at ibpc.fr> wrote:
> >
> > Well sorry about that but it seems I was wrong.
> > It was Friday evening and I guess I've not been careful.
> >
> > Actually when you specify nargs="?",  the doc says "One argument will be consumed from the command line if possible, and produced as a single item".
> > So you can't pass several arguments to the program.
> 
> Right below that in the docs it explains about using nargs='*' and nargs='+'. One of those will do what you want.
> 
> Oscar.
> 
> >
> > So, to rephrase the question, how can I get a argument parser that parses the command-line just as Unix grep would do?
> > i.e.
> >
> > $ echo 42 > foo.txt
> > $ echo 172 >> foo.txt
> > $ cp foo.txt bar.txt
> > $
> > $ grep 42 foo.txt
> > 42
> > $ grep 42 foo.txt bar.txt
> > foo.txt:42
> > bar.txt:42
> > $ cat foo.txt | grep 42
> > 42
> > $ grep -c 42 foo.txt
> > 1
> >
> >
> > Cheers,
> > Ben
> >
> >
> >
> >
> > Le Jul 27, 2012 à 7:08 PM, Benoist Laurent a écrit :
> >
> >>
> >>
> >> Yes basically looks like you get it.
> >> I have to further test it but my first impression is that it's correct.
> >>
> >> So actually the point was to use nargs="?".
> >>
> >> Thank you very much.
> >> Ben
> >>
> >>
> >>
> >> Le Jul 27, 2012 à 5:44 PM, Peter Otten a écrit :
> >>
> >>> Benoist Laurent wrote:
> >>>
> >>>> I'm impletting a tool in Python.
> >>>>
> >>>> I'd like this tool to behave like a standard unix tool, as grep for
> >>>>
> >>>> exemple. I chose to use the argparse module to parse the command line and
> >>>>
> >>>> I think I'm getting into several limitations of this module.
> >>>>
> >>>>
> >>>>> First Question.
> >>>>
> >>>> How can I configure the the ArgumentParser to allow the user to give
> >>>>
> >>>> either an input file or to pipe the output from another program?
> >>>>
> >>>>
> >>>> $ mytool.py file.txt
> >>>>
> >>>> $ cat file.txt | mytool.py
> >>>
> >>>
> >>> $ echo alpha > in.txt
> >>> $ cat in.txt | ./mytool.py 
> >>> ALPHA
> >>> $ cat in.txt | ./mytool.py - out.txt
> >>> $ cat out.txt 
> >>> ALPHA
> >>> $ ./mytool.py in.txt 
> >>> ALPHA
> >>> $ ./mytool.py in.txt out2.txt
> >>> $ cat out2.txt 
> >>> ALPHA
> >>> $ cat ./mytool.py
> >>> #!/usr/bin/env python
> >>> assert __name__ == "__main__"
> >>>
> >>> import argparse
> >>> import sys
> >>>
> >>> parser = argparse.ArgumentParser()
> >>> parser.add_argument("infile", nargs="?", type=argparse.FileType("r"), 
> >>> default=sys.stdin)
> >>> parser.add_argument("outfile", nargs="?", type=argparse.FileType("w"), 
> >>> default=sys.stdout)
> >>> args = parser.parse_args()
> >>>
> >>> args.outfile.writelines(line.upper() for line in args.infile)
> >>>
> >>> Is that good enough?
> >>>
> >>>
> >>> -- 
> >>> http://mail.python.org/mailman/listinfo/python-list
> >>>
> >>
> >> -- 
> >> Benoist Laurent
> >> Laboratoire de Biochimie Theorique / CNRS UPR 9080
> >> Institut de Biologie Physico-Chimique
> >> 13, rue Pierre et Marie Curie
> >> F-75005 Paris
> >> Tel. +33 [0]1 58 41 51 67 or +33 [0]6 21 64 50 56
> >>
> >> -- 
> >> http://mail.python.org/mailman/listinfo/python-list
> >
> >
> > -- 
> > Benoist Laurent
> > Laboratoire de Biochimie Theorique / CNRS UPR 9080
> > Institut de Biologie Physico-Chimique
> > 13, rue Pierre et Marie Curie
> > F-75005 Paris
> > Tel. +33 [0]1 58 41 51 67 or +33 [0]6 21 64 50 56
> >
> >
> > --
> > http://mail.python.org/mailman/listinfo/python-list
> >

-- 
Benoist Laurent
Laboratoire de Biochimie Theorique / CNRS UPR 9080
Institut de Biologie Physico-Chimique
13, rue Pierre et Marie Curie
F-75005 Paris
Tel. +33 [0]1 58 41 51 67 or +33 [0]6 21 64 50 56

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