singledispatch-method / E1519

Message emitted:

singledispatch decorator should not be used with methods, use singledispatchmethod instead.

Description:

singledispatch should decorate functions and not class/instance methods. Use singledispatchmethod for those cases.

Problematic code:

from functools import singledispatch


class Board:
    @singledispatch  # [singledispatch-method]
    def convert_position(self, position):
        pass

    @convert_position.register  # [singledispatch-method]
    def _(self, position: str) -> tuple:
        position_a, position_b = position.split(",")
        return (int(position_a), int(position_b))

    @convert_position.register  # [singledispatch-method]
    def _(self, position: tuple) -> str:
        return f"{position[0]},{position[1]}"

Correct code:

from functools import singledispatch


@singledispatch
def convert_position(position):
    print(position)


@convert_position.register
def _(position: str) -> tuple:
    position_a, position_b = position.split(",")
    return (int(position_a), int(position_b))


@convert_position.register
def _(position: tuple) -> str:
    return f"{position[0]},{position[1]}"

Created by the stdlib checker.