Python argparse: Too few arguments

Question

I'm trying to use the argparse library in Python. I want to have the user do something like:

python my_script.py csv_name.csv [--dryrun]

where --dryrun is an optional parameter.

I then have the user enter an API key and secret key. When I run my code, I get past entering the API and secret keys and then I get:

usage: my_script.py [-h] csv dryrun
salesforceImporter.py: error: too few arguments

Here's my code:

def main():
    api_key = getpass.getpass(prompt='Enter API Key: ')
    secret_key = getpass.getpass(prompt='Enter Secret Key: ')

    parser = argparse.ArgumentParser()
    parser.add_argument("csv")
    parser.add_argument("dryrun")
    args = parser.parse_args()

    validate_csv_name(args.csv)

    is_dry_run = args.dryrun == '--dryrun'

Any idea where I'm going wrong?

Thanks!

Answer 1

When you use the following syntax:

parser.add_argument("csv")
parser.add_argument("dryrun")

You're adding these as positional -- required -- arguments. Only arguments with a leading dash or two are optional.

See the docs here:

The add_argument() method must know whether an optional argument, like -f or --foo, or a positional argument, like a list of filenames, is expected. The first arguments passed to add_argument() must therefore be either a series of flags, or a simple argument name. For example, an optional argument could be created like:

>>> parser.add_argument('-f', '--foo')

Answer 2

To add an optional --dry-run argument, you may use the following snippet:

parser.add_argument('--dry-run', action='store_true')

Calling your script using python my_script.py csv_name.csv --dry-run will result to args.dry_run being True. Not putting the option will result to it being False