如何检测何时调用了“--help”？

Question

My Click 7.0 application has one group, having multiple commands, called by the main cli function like so:

import click

@click.group()
@click.pass_context
def cli(ctx):
   "This is cli helptext"

    click.echo('cli called')
    click.echo('cli args: {0}'.format(ctx.args))

@cli.group(chain=True)
@click.option('-r', '--repeat', default=1, type=click.INT, help='repeat helptext')
@click.pass_context
def chainedgroup(ctx, repeat):
    "This is chainedgroup helptext"

    for _ in range(repeat):
        click.echo('chainedgroup called')
    click.echo('chainedgroup args: {0}'.format(ctx.args))

@chainedgroup.command()
@click.pass_context
def command1(ctx):
    "This is command1 helptext"

    print('command1 called')
    print('command1 args: {0}'.format(ctx.args))

@chainedgroup.command()
@click.pass_context
def command2(ctx):
    "This is command2 helptext"

    print('command2 called')
    print('command2 args: {0}'.format(ctx.args))

Run:

$ testcli --help
$ testcli chainedgroup --help
$ testcli chainedgroup command1 --help

The help-text displays as expected--except that the parent functions are inadvertently run in the process. A single conditional checking to see if '--help' is contained in ctx.args should be enough to solve this problem, but does anyone know how/when '--help' is passed? Because with this code, ctx.args is empty every time.

Answer 1

If argparse is not an option, how about:

if '--help' in sys.argv:
...

Answer 2

click stores the arguments passed to a command in a list. The method get_os_args() returns such list. You can check if --help is in that list to determine if the help flag was invoked. Something like the following:

if '--help' in click.get_os_args():
    pass

Answer 3

It is prebuilt - Click looks like a decorator for argparse (Hurrah for common sense).

import click

@click.command()
@click.option('--count', default=1, help='Number of greetings.')
@click.option('--name', prompt='Your name',
              help='The person to greet.')
def hello(count, name):
    """Simple program that greets NAME for a total of COUNT times."""
    for x in range(count):
        click.echo('Hello %s!' % name)

if __name__ == '__main__':
    hello()

So you can write

python cl.py --name bob

And see

Hello bob!

Help is already done (as it is argparse)

python cl.py --help
Usage: cl.py [OPTIONS]

  Simple program that greets NAME for a total of COUNT times.

Options:
  --count INTEGER  Number of greetings.
  --name TEXT      The person to greet.
  --help           Show this message and exit.

Been busy only just had time to read into this.

Sorry for the delay

Answer 4

Why not use argparse ? It has excellent for CLI parsing.