Argparse - error handling the required argument

Question

I have a script which basically asks the user for the argument to be passed to the program as below:

parser = argparse.ArgumentParser()
parser.add_argument("-t" , required = True)
args , unknown = parser.parse_known_args()

#rest of the code

Now I wanna do error handling so it shows the message I want and run the functions I want in case the user didn't enter the argument or entered it incorrectly. I have tried putting everything in try and except however I couldn't find the proper error type to do it for me

try: 
  parser = argparse.ArgumentParser()
  parser.add_argument("-t" , required = True)
  args , unknown = parser.parse_known_args()

  #rest of the code
except argparse.ArgumentError:
   myfunc()

However, this way if I get any other errors in my code, it still caught here and not in their own try and except.

Possible [solution](https://stackoverflow.com/questions/5943249/python-argparse-and-controlling-overriding-the-exit-status-code) — sudden_appearance, Feb 15 '22 at 14:28
Omit the `required` and do your own `if args.t is None:` test after parsing. — hpaulj, Feb 15 '22 at 16:46

score 1 · Answer 1 · answered Feb 15 '22 at 14:34

Argparse raises a SystemExit when a required argument is missing. You could use the else clause in the try/except to execute the rest of your code only if the arguments were parsed correctly:

try: 
    parser = argparse.ArgumentParser()
    parser.add_argument("-t" , required = True)
    args , unknown = parser.parse_known_args()
except SystemExit:
    func_for_wrong_args()
else:
    func_for_correct_args()

score 0 · Answer 2 · answered Jul 08 '23 at 08:45

0

Use assert, it comes with a print message.

assert args.t, "Argument --t is required"

answered Jul 08 '23 at 08:45

Bryan Laygond

63
4

Argparse - error handling the required argument

2 Answers2