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Click - command line arguments in python

I only found out about click last month. I am surprised because it is the 15th most downloaded package on pypi at time of writing.

Let us see what it is…

What is click?#

Click is a Python package for creating beautiful command line interfaces in a composable way with as little code as necessary

It features:

  • Arbitrary nesting of commands
  • Automatic help page generation
  • Supports lazy loading of subcommands at runtime


pip install click


The module:

import click

@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 _ in range(count):
        click.echo("Hello, %s!" % name)

if __name__ == '__main__':

Calling it:

$ python --count=3
Your name: John
Hello John!
Hello John!
Hello John!

Getting help:

$ python --help
Usage: [OPTIONS]

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

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

Why Click?#

There are other libraries - like argparse in the standard library, optparse or docopt

There is no single cli utility for python that does all of this:

  • lazily composable without restrictions (what the hell does that mean?)
  • Support implementation of Unix/POSIX command line conventions. Posix are standards for portable operating system interfaces
  • Supports loading values from environment variables out of the box
  • Support for prompting of custom values
  • Is fully nestable and composable
  • Supports file handling out of the box
  • Comes with useful common helpers (getting terminal dimensions, ANSI colors, fetching direct keyboard input, screen clearing, finding config paths, launching apps and editors, etc.).

Click promises multiple Click instances will continue to function as intended when strung together

Click is internally based on optparse instead of argparse.