Python argparse: command-line argument that can be either named or positional

Question

I am trying to make a Python program that uses the argparse module to parse command-line options.

I want to make an optional argument that can either be

Answer 1

Try to use the "nargs" parameter of the add_argument methode. This way it works for me. Now you can add the username twice, so you have to check it and raise an error, if you want.

import argparse
if __name__ == '__main__':
   parser = argparse.ArgumentParser()
   parser.add_argument("-u", "--user-name", default="admin")
   parser.add_argument("user_name", default="admin", nargs="?")
   args = parser.parse_args()
   print(args)