Default argparse values

Question

I have a script where the user can input two date values for a date range to run my script. If they don't input two values, I want my script to run with a default date range. How can I do this?

Right now this is what I have:

parser = argparse.ArgumentParser()
parser.add_argument('start', type=str, help='Start date YYYY-MM-DD')
parser.add_argument('end', type=str, help='End date YYYY-MM-DD')
args = parser.parse_args()

start = args.start
stop = args.end

** if the two dates are invalid or not provided by user: ** 
start = '20220101'
stop = '20220416'

parser.add_argument('end', type=str, help='End date YYYY-MM-DD', default='2022-10-05)` — Bes Dollma
– Bes Dollma, Commented Aug 5, 2022 at 15:35
This gets tricky, as you can't get a default start without using the default end, as myscript 20220805 will assume it was given a starting date. — chepner
– chepner, Commented Aug 5, 2022 at 15:47

fed · Accepted Answer · 2022-08-05 15:37:04Z

3

you can use the argument default

parser = argparse.ArgumentParser()
parser.add_argument('start', type=str, default='20220101', help='Start date YYYY-MM-DD')
parser.add_argument('end', type=str, default='20220416', help='End date YYYY-MM-DD')
args = parser.parse_args()

start = args.start
stop = args.end

answered Aug 5, 2022 at 15:37

fed

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1 Comment

chepner Over a year ago

Specifying a default argument isn't sufficient, You also need to use nargs='?', as positional parameters are required by default.

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