Class Converter

src/attr/_make.py:3087–3182

Stores a converter callable. Allows for the wrapped converter to take additional arguments. The arguments are passed in the order they are documented. Args: converter (Callable): A callable that converts the passed value. takes_self (bool): Pass the pa

class Converter:
    """
    Stores a converter callable.

    Allows for the wrapped converter to take additional arguments. The
    arguments are passed in the order they are documented.

    Args:
        converter (Callable): A callable that converts the passed value.

        takes_self (bool):
            Pass the partially initialized instance that is being initialized
            as a positional argument. (default: `False`)

        takes_field (bool):
            Pass the field definition (an :class:`Attribute`) into the
            converter as a positional argument. (default: `False`)

    .. versionadded:: 24.1.0
    """

    __slots__ = (
        "__call__",
        "_first_param_type",
        "_global_name",
        "converter",
        "takes_field",
        "takes_self",
    )

    def __init__(self, converter, *, takes_self=False, takes_field=False):
        self.converter = converter
        self.takes_self = takes_self
        self.takes_field = takes_field

        ex = _AnnotationExtractor(converter)
        self._first_param_type = ex.get_first_param_type()

        if not (self.takes_self or self.takes_field):
            self.__call__ = lambda value, _, __: self.converter(value)
        elif self.takes_self and not self.takes_field:
            self.__call__ = lambda value, instance, __: self.converter(
                value, instance
            )
        elif not self.takes_self and self.takes_field:
            self.__call__ = lambda value, __, field: self.converter(
                value, field
            )
        else:
            self.__call__ = self.converter

        rt = ex.get_return_type()
        if rt is not None:
            self.__call__.__annotations__["return"] = rt

    @staticmethod
    def _get_global_name(attr_name: str) -> str:
        """