Default Values

To use default values, just add a default value to the attribute

import attr

from clime import clime


@attr.s(auto_attribs=True)
class Dude:
    name: str = "joe"  # attributes with default values in the class will be set as optional arguments in the cli

    def state_name(self):
        print(f"hi! my name is {self.name}")


def main():
    clime(Dude).state_name()


if __name__ == "__main__":
    main()

Check it:

$ python tutorial_002.py --help

usage: tutorial_002.py [-h] [--name NAME]

optional arguments:
  -h, --help   show this help message and exit
  --name NAME  (default: joe)

Super!

Name is now a positional argument with a defaul value. The default value is added to the --help.

Try it!

$ python tutorial_002.py
hi! my name is joe

It works with defaults!

$ python tutorial_002.py --name mike
hi! my name is mike

It works with optional arguments!

Want to know what will not work? Positional arguments:

$ python tutorial_002.py mike
usage: tutorial_002.py [-h] [--name NAME]
tutorial_002.py: error: unrecognized arguments: mike

Note that this is an unfortunate difference between argument parser and the underlying class init. The class can attributes with default argument as positional. Argument parser cannot.

Anyways... that's it. All you need to take use default values is give the attribute a default value!