Documenting Scripts

Click makes it very easy to document your command line tools. First of all, it automatically generates help pages for you. While these are currently not customizable in terms of their layout, all of the text can be changed.

Help Texts

Commands and options accept help arguments. In the case of commands, the docstring of the function is automatically used if provided.

Simple example:

@click.command()
@click.option('--count', default=1, help='number of greetings')
@click.argument('name')
def hello(count, name):
    """This script prints hello NAME COUNT times."""
    for x in range(count):
        click.echo('Hello %s!' % name)

And what it looks like:

$ hello --help
Usage: hello [OPTIONS] NAME

  This script prints hello NAME COUNT times.

Options:
  --count INTEGER  number of greetings
  --help           Show this message and exit.

Arguments cannot be documented this way. This is to follow the general convention of Unix tools of using arguments for only the most necessary things and to document them in the introduction text by referring to them by name.

Preventing Rewrapping

The default behavior of Click is to rewrap text based on the width of the terminal. In some circumstances, this can become a problem. The main issue is when showing code examples, where newlines are significant.

Rewrapping can be disabled on a per-paragraph basis by adding a line with solely the \b escape marker in it. This line will be removed from the help text and rewrapping will be disabled.

Example:

@click.command()
def cli():
    """First paragraph.

    This is a very long second paragraph and as you
    can see wrapped very early in the source text
    but will be rewrapped to the terminal width in
    the final output.

    \b
    This is
    a paragraph
    without rewrapping.

    And this is a paragraph
    that will be rewrapped again.
    """

And what it looks like:

$ cli --help
Usage: cli [OPTIONS]

  First paragraph.

  This is a very long second paragraph and as you can see wrapped very early
  in the source text but will be rewrapped to the terminal width in the final
  output.

  This is
  a paragraph
  without rewrapping.

  And this is a paragraph that will be rewrapped again.

Options:
  --help  Show this message and exit.

Meta Variables

Options and parameters accept a metavar argument that can change the meta variable in the help page. The default version is the parameter name in uppercase with underscores, but can be annotated differently if desired. This can be customized at all levels:

@click.command(options_metavar='<options>')
@click.option('--count', default=1, help='number of greetings',
              metavar='<int>')
@click.argument('name', metavar='<name>')
def hello(count, name):
    """This script prints hello <name> <int> times."""
    for x in range(count):
        click.echo('Hello %s!' % name)

Example:

$ hello --help
Usage: hello <options> <name>

  This script prints hello <name> <int> times.

Options:
  --count <int>  number of greetings
  --help         Show this message and exit.

Command Short Help

For commands, a short help snippet is generated. By default, it’s the first sentence of the help message of the command, unless it’s too long. This can also be overridden:

@click.group()
def cli():
    """A simple command line tool."""

@cli.command('init', short_help='init the repo')
def init():
    """Initializes the repository."""

@cli.command('delete', short_help='delete the repo')
def delete():
    """Deletes the repository."""

And what it looks like:

$ repo.py
Usage: repo.py [OPTIONS] COMMAND [ARGS]...

  A simple command line tool.

Options:
  --help  Show this message and exit.

Commands:
  delete  delete the repo
  init    init the repo

Help Parameter Customization

New in version 2.0.

The help parameter is implemented in Click in a very special manner. Unlike regular parameters it’s automatically added by Click for any command and it performs automatic conflict resolution. By default it’s called --help, but this can be changed. If a command itself implements a parameter with the same name, the default help parameter stops accepting it. There is a context setting that can be used to override the names of the help parameters called help_option_names.

This example changes the default parameters to -h and --help instead of just --help:

CONTEXT_SETTINGS = dict(help_option_names=['-h', '--help'])

@click.command(context_settings=CONTEXT_SETTINGS)
def cli():
    pass

And what it looks like:

$ cli -h
Usage: cli [OPTIONS]

Options:
  -h, --help  Show this message and exit.