Dude about argparse library [python] [duplicate]

Question

I know get values from argsparse like:

parser.add_argument('--volume', help='Ejecuta una aplicacion cualquiera')

Also I know if the argument is True or False with this:

parser.add_argument('--getVolume', action='store_true', help='Ejecuta una aplicacion cualquiera')

But I don't Know use both some time, because I want use the argument like getter-setter. For example if I dont write a number the program return the current volume and if I write a number the app set this volume to the robot.

python app.py --volume      # Return the current volume
python app.py --volume 80   # Set the volume to the 80%

Thank you very much,

Carlos.

In addition to the link, use such a default that you can then decide whether to display or update the volume. — Ilja Everilä
– Ilja Everilä, Commented Mar 3, 2017 at 9:24
docs.python.org/3/library/argparse.html Look example 16.4.3.2 — Serenity
– Serenity, Commented Mar 3, 2017 at 9:25

Stefan Jaritz · Accepted Answer · 2017-03-03 09:26:44Z

0

You can use the default value for the set/get checking. Some pseudo code:

parser.add_argument("-v", "--vol", dest="vol",  
    help="the volume [default: %(default)s]",
    default=None
)
args = parser.parse_args()

if None == args.vol:
    print(str(getVolume()))
else:
    setVolume(float(args.vol))

answered Mar 3, 2017 at 9:26

Stefan Jaritz

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4 Comments

Ilja Everilä Over a year ago

While this works, it'll always either get or set. Using nargs='?' with const=... would make it truly optional, if needed.

elena Over a year ago

You aren't taken into account the case when the user enters --vol without specifying a value for it.

Stefan Jaritz Over a year ago

this is a pseudo code. Feel free to change it. I would serve that problem in the way when no params are put on the commandline the programm is in get mode. If there is a volume parameter it is in set mode

Carlos Barreiro Mata Over a year ago

Thank you! The problem was that of this way I need if the argument volume exists. I solved my problem with: parser.add_argument('--volume', help='Ejecuta una aplicacion cualquiera', nargs='?', const='get'). Of this form if the argument volume don't exist the value is None, if the argument volume exist but it haven't value the value is 'get'. Thank you, very much.

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