How to parse on/off (debug) flag using argparse?

argparse, python

Solution

Use the `store_true` action instead:

parser.add_argument(
    '--debug',
    action='store_true', 
    help='print debug messages to stderr'
)

`nargs='?'` should only be used for options that take one or more arguments (with a fallback to a default value).

Problem

My CLI program uses a `--debug` flag to decide whether or not to print debug messages. When `--debug` is specified, it should print debug messages; otherwise, it should not print debug messages. My current approach is: `parser.add_argument('--debug', help='print debug messages to stderr', nargs='?')` However, the `--help` message suggests that this approach does not achieve my goal: ``` optional arguments: -h, --help show this help message and exit --debug [DEBUG] print debug messages to stderr ``` As you can see, it wants a value after the flag; however, `--debug` is an on/off argument. What should I do instead?

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