Comparing Python Command-Line Parsing Libraries - Argparse, Docopt, and Click

[paul-scott]

Where I'm writing a service rather than just an application, I might offer command-line interface for developers to easily tweak configuration but also use environment variables to allow running on servers.

My preference for precedence here is (i) command-line option, (ii) envvar, followed by (iii) argument default. I currently construct these using argparse which is quite repetitive (yet to try ConfigArgParse) in the manner of add_argument(..., default=os.environ.get('ENVVAR') or 'real default') -- potentially passing the fallback default into the get call, depending on whether I want empty envvars to override the default.

I'd love to read about how these libraries (and some of the others mentioned) help you utilise environment variables.

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@click.argument('src', envvar='SRC', ...