Method __new__

example_code/item_062.py:192–197

(meta, name, bases, class_dict)

class ValidateFilledPolygon(ValidatePolygon):
    def __new__(meta, name, bases, class_dict):
        # Only validate non-root classes
        if not class_dict.get("is_root"):
            if class_dict["color"] not in ("red", "green"):
                raise ValueError("Fill color must be supported")
        return super().__new__(meta, name, bases, class_dict)

class FilledPolygon(Polygon, metaclass=ValidateFilledPolygon):
    is_root = True