ArgParse: Check if argument value present or not, else use default

Question

I want to store TRUE/FALSE when the parameters are passed in the command line. But if nothing is present after the parameter name or the parameter isn't specified, it should store TRUE. The code below does it for the most part, except that it stores NONE when simply --stoplogging is specified (as in 2nd desired output)

import argparse
parser=argparse.ArgumentParser()
parser.add_argument('--stoplogging', action='store', default="True", nargs='?')
args=parser.parse_args()
print(args)

Actual Output:

>>>python test.py
>>>Namespace(stoplogging='True')

>>>python test.py  --stoplogging
>>>Namespace(stoplogging='None')

>>>python test.py  --stoplogging=True
>>>Namespace(stoplogging='True')

>>>python test.py  --stoplogging=False
>>>Namespace(stoplogging='False')

Desired output:

>>>python test.py
>>>Namespace(stoplogging='True')

>>>python test.py  --stoplogging
>>>Namespace(stoplogging='True')

>>>python test.py  --stoplogging=True
>>>Namespace(stoplogging='True')

>>>python test.py  --stoplogging=False
>>>Namespace(stoplogging='False')

What output do you get with your code? Edit it into the question. — DisappointedByUnaccountableMod, May 05 '21 at 06:37
You may be looking for `action="store_true"` - This means that, if the option is specified, assign the value `True`. Otherwise it's set to `False` — rdas, May 05 '21 at 06:38
When I use ```action="store_true"``` I get the following: usage: test.py [-h] [--stoplogging] test.py: error: argument --stoplogging: ignored explicit argument 'False' — Chris Chance, May 05 '21 at 06:39

score 1 · Answer 1 · answered May 05 '21 at 06:49

I have found a solution that fits my desired output:

import argparse
parser=argparse.ArgumentParser()
parser.add_argument('--stoplogging', action='store', default="True", const="True", nargs="?")
args=parser.parse_args()
print(args)

nargs='?' means 0-or-1 arguments
const="True" sets the default to True when there are 0 arguments

ArgParse: Check if argument value present or not, else use default

1 Answers1