__init__.py 文件源码

def __new__(cls, class_name, bases, attrs):
        new_class = type.__new__(cls, class_name, bases, attrs)

        # If new_class has no __delegate_class__, then it's a base like
        # MotorClientBase; don't try to update its attrs, we'll use them
        # for its subclasses like MotorClient.
        if getattr(new_class, '__delegate_class__', None):
            for base in reversed(inspect.getmro(new_class)):
                # Turn attribute factories into real methods or descriptors.
                for name, attr in base.__dict__.items():
                    if isinstance(attr, MotorAttributeFactory):
                        new_class_attr = attr.create_attribute(new_class, name)
                        setattr(new_class, name, new_class_attr)

        return new_class