How to set default value of option to another argument in Python Click?

Question

Is it possible to define an option's default value to another argument in click?

What I'd like would be something like:

@click.command()
@click.argument('project')
@click.option('--version', default=project)
def main(project, version):
  ...

If the option --version is empty, it would automatically take project's value. Is something like this possible?

Fung

Is you code not working? – Apteryx

Yes, this is entirely possible, however you can't then use variables from functions in your @click.option - you'd need to define project before @click.option. – Sunless

@YashKrishan no the code is not working – Fung

Is there an error? If yes, share it – Apteryx

Answer 1

You could try setting version to None. If the user sets it, it will be overridden, but if they do not you set it to project within the main function.

@click.command()
@click.argument('project')
@click.option('--version', default=None)
def main(project, version):
    if version is None:
        version = project
    print("proj", project, "vers", version)

if __name__ == "__main__":
    main()

Example usage:

$ python3 clicktest.py 1
proj 1 vers 1
$ python3 clicktest.py 1 --version 2
proj 1 vers 2

To do this in the decorators, you can take advantage of the callback option, which accepts (context, param, value):

import click

@click.command()
@click.argument('project')
@click.option('--version', default=None,
              callback=lambda c, p, v: v if v else c.params['project'])
def main(project, version):
    print("proj", project, "vers", version)


if __name__ == "__main__":
    main()

Auxiliary

Yes but I would like a solution where everything is in the Click decorators and not inside the function – Fung