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with argparse, is it possible to check whether the first positional argument has been entered:

import argparse

if __name__ == "__main__":

    parser = argparse.ArgumentParser()
    parser.add_argument("object_type", type=str)
    parser.add_argument("--pass1", type=str)
    parser.add_argument("--pass2", type=str)

    args = parser.parse_args()

    print(args)

when calling: myscript.py --pass1=foo, I get the error: error: the following arguments are required: object_type

what makes sense, but there don't seem to be a way to catch the error beforehand.

Something like:

if args.object_type is None:
    raise argparse.ArgumentError(message="object_type must be defined!")

tried also with try/except with no luck.

possible or not ?

Improve this question
6
  • Yeah, when you fail to give it the required arguments it returns on a sys.exit(2) from argparse itself and there's no way to catch that... probably. Commented May 15, 2024 at 15:42
  • Ok, I found a duplicate question The way to bypass the required positional is to add the kwarg nargs='?' to the positional add_argument. Then, you'll need to check using some other means Commented May 15, 2024 at 15:47
  • Does this answer your question? Argparse optional positional arguments? Commented May 15, 2024 at 15:48
  • actually not, since my positional argument is not optional. Unless positional forcibly means mandatory Commented May 15, 2024 at 16:03
  • The docs talk about changing the parser.error and parser.exit methods to capture an error., keeping it from exiting. There is also an exit_on_error parameter, but that may not work with this error, since it isn't redirecting a ArgumentError incident. Commented May 15, 2024 at 16:19
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