Method _deserialize

src/marshmallow/fields.py:866–891

(
        self,
        value: typing.Any,
        attr: str | None,
        data: typing.Mapping[str, typing.Any] | None,
        **kwargs,
    )

        )

    def _deserialize(
        self,
        value: typing.Any,
        attr: str | None,
        data: typing.Mapping[str, typing.Any] | None,
        **kwargs,
    ) -> tuple:
        if not utils.is_sequence_but_not_string(value):
            raise self.make_error("invalid")

        self.validate_length(value)

        result = []
        errors = {}

        for idx, (field, each) in enumerate(zip(self.tuple_fields, value, strict=True)):
            try:
                result.append(field.deserialize(each, **kwargs))
            except ValidationError as error:
                if error.valid_data is not None:
                    result.append(error.valid_data)
                errors.update({idx: error.messages})
        if errors:
            raise ValidationError(errors, valid_data=result)

        return tuple(result)


class String(Field[str]):