Looks like a nice wrapper around argparse: https://docs.python.org/3/library/argparse.html
I'm curious about that decision given that optparse is deprecated. It says it's because argparse doesn't allow nested commands, but I don't really see why that feature is so desirable as to warrant using a deprecated module. I probably need to have a play with it to find out.
Looks like a nice module.
argparse requires the parser to have full knowledge of everything which makes it slow if you add many commands. Biggest problem though is that it's parsing system is a bit broken when it comes to escaping. Options with arguments cannot have values starting with dashes which is problematic for delegating subcommands to other things.
For what I wrote Click for I could not find any alternatives that worked that way besides optparse itself but that is hard to use.
Links to some open bugs on it:
* http://bugs.python.org/issue13966
* http://bugs.python.org/issue14191