False Positive In String Formatter

[jbylund]

Running vulture over

from string import Formatter

class StrictFormatter(Formatter):
    def check_unused_args(self, used_args, _args, kwargs):
        """Raise exception if any keyword arguments are unused."""
        unused_kwargs = set(kwargs) - set(used_args)
        if unused_kwargs:
            raise AssertionError(
                "{} {} not used in formatting string.".format(
                    sorted(unused_kwargs),
                    ["was", "were"][min(1, len(unused_kwargs)-1)]
                )
            )

def main():
    StrictFormatter().format("xxx", foo="foo")

if "__main__" == __name__:
    main()

gives

vulture_check.py:4: unused function 'check_unused_args' (60% confidence)

but when you run it you see that the code is in fact being exercised. Thoughts?

[jendrikseipp]

Thanks for the report! Static analyzers like Vulture can't detect this kind of code use. Instead, we'll have to add a whitelist for the methods of string.Formatter (https://docs.python.org/3/library/string.html).