CODEWITHSUNDEEP
pythonpython-3.xargumentsargparsesubcommand
Rietty
Rietty

Reputation: 1156

How to have a specific sub-command require flag with argparse?

so I am writing a python script that uses argparse in order to pass information and process input. I have been using sub-commands to force/use different operations in the program. So far my script is formatted like so:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import argparse

def main(username, password, api, apiId):
    print("Hello, world!")

def _cli():
    # Create parser to obtain arguments
    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.ArgumentDefaultsHelpFormatter, argument_default=argparse.SUPPRESS)
    subparsers = parser.add_subparsers(dest = "api", required = True)
    base_subparser = argparse.ArgumentParser(add_help = False)
    # Shared arguments
    base_subparser.add_argument('-u', '--username', help = "Username", default = "admin")
    base_subparser.add_argument('-p', '--password', help = "Password", default = "admin")

    # Create subcommands
    create_parser = subparsers.add_parser("create", parents = [base_subparser])
    update_parser = subparsers.add_parser("update", parents = [base_subparser])

    # Flag for sub-parser to pass API ID
    update_parser.add_argument('-i', '--apiId', help = "ID for API you are trying to access.", required = True)

    # Obtain all the argument values
    args = parser.parse_args()

    # Return them in a dictionary format
    return vars(args)

if __name__ == '__main__':
    # Pass arguments to main function using dictonary format.
    main(**_cli())

Where usage is specified as such:

usage: test.py [-h] {create,update} ...

positional arguments: {create, update}

optional arguments: -h, --help show this help message and exit

My issue is that while the update command is working fine, where I am required to pass an ID, my create has a bug/issue where it complains about not setting the flag/passing one even though it is not required/needed.

main(**_cli())
TypeError: main() missing 1 required positional argument: 'apiId'

What am I doing wrong here and how do I fix it? I've tried to google but I can't seem to understand the problem/how to resolve it.

Upvotes: 1

Views: 658

Answers (1)

Alex
Alex

Reputation: 7045

The error you are getting is telling you that apiId is not being provided when you are using the create subcommand. You can either specify a default parameter, like so:

def main(username, password, api, apiId=None):
    print("API: {}".format(api))
    print("API ID: {}".format(apiId))

~ python args.py create -u a -p b
API: create
API ID: None
~ python args.py update -u a -p b -i c
API: update
API ID: c

or you could get a dict of keyword arguments using ** expansion in the function definition:

def main(**kwds):
    print(kwds)

~ python args.py create -u a -p b
{'api': 'create', 'username': 'a', 'password': 'b'}
~ python args.py update -u a -p b -i c
{'api': 'update', 'username': 'a', 'password': 'b', 'apiId': 'c'}

Upvotes: 1

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