Using Boolean Flags in Python Click Library (command line arguments)

So click is not simply a command line parser. It also dispatches and processes the commands. So in your example, the log() function never returns to main(). The intention of the framework is that the decorated function, ie: log(), will do the needed work.

Code:

import click

@click.command()
@click.option('--verbose', '-v', is_flag=True, help="Print more output.")
def log(verbose):
    click.echo("Verbose {}!".format('on' if verbose else 'off'))


def main(*args):
    log(*args)

Test Code:

if __name__ == "__main__":
    commands = (
        '--verbose',
        '-v',
        '',
        '--help',
    )

    import sys, time

    time.sleep(1)
    print('Click Version: {}'.format(click.__version__))
    print('Python Version: {}'.format(sys.version))
    for cmd in commands:
        try:
            time.sleep(0.1)
            print('-----------')
            print('> ' + cmd)
            time.sleep(0.1)
            main(cmd.split())

        except BaseException as exc:
            if str(exc) != '0' and \
                    not isinstance(exc, (click.ClickException, SystemExit)):
                raise

Results:

Click Version: 6.7
Python Version: 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]
-----------
> --verbose
Verbose on!
-----------
> -v
Verbose on!
-----------
> 
Verbose off!
-----------
> --help
Usage: test.py [OPTIONS]

Options:
  -v, --verbose  Print more output.
  --help         Show this message and exit.