too-many-positional-arguments / R0917

Message emitted:

Too many positional arguments (%s/%s)

Description:

Used when a function has too many positional arguments.

Problematic code:

class FiveArgumentMethods:
    """The max positional arguments default is 5."""

    def take_five_args(self, a, b, c, d, e):  # [too-many-positional-arguments]
        pass

Correct code:

class FiveArgumentMethods:
    """The max positional arguments default is 5."""

    def take_five_args(self, a, b, c, d, *, e=False):
        pass

Configuration file:

[MESSAGES CONTROL]
disable=too-many-arguments

Additional details:

Positional arguments work well for cases where the the use cases are self-evident, such as unittest's assertEqual(first, second, msg=None). Comprehensibility suffers beyond a handful of arguments, though, so for functions that take more inputs, require that additional arguments be passed by keyword only by preceding them with *:

def make_noise(self, volume, *, color=noise.PINK, debug=True):
    ...

Related links:

• Ruff discussion

• Pylint issue

Created by the design checker.