key=value style command argument parser

[snippsat]

A example with Click.

# dig.py
import click

@click.command()
@click.option('--hash', type=click.Choice(['MD5', 'SHA1'], case_sensitive=False))
def digest(hash):
    click.echo(f'Your choice is <{hash}>')

if __name__ == '__main__':
    digest()

Output:
E:\div_code
λ python dig.py --hash=MD5
Your choice is <MD5>

E:\div_code
λ python dig.py --hash=SHA1
Your choice is <SHA1>

E:\div_code
λ python dig.py --hash=foo
Usage: dig.py [OPTIONS]
Try "dig.py --help" for help.

Error: Invalid value for "--hash": invalid choice: foo. (choose from MD5, SHA1)

E:\div_code
λ python dig.py --help
Usage: dig.py [OPTIONS]

Options:
  --hash [MD5|SHA1]
  --help             Show this message and exit.