For Python, I've standardize on click.
It provides simple decorator to turn functions into commands, sub-commands, etc, with easy options and built-in help.
I was using click, but it requires too much boilerplate. Fire is much simpler to use, just as powerful (or maybe 95% as powerful) and it's developed by Google devs (it's not an official Google project as far as I remember), so it seems of reasonable quality.