django的orm--contenttype操作

class PricePolicy(models.Model):
    """价格与有课程效期表"""
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey(‘content_type‘, ‘object_id‘)

    valid_period_choices = ((1, ‘1天‘), (3, ‘3天‘),
                            (7, ‘1周‘), (14, ‘2周‘),
                            (30, ‘1个月‘),
                            (60, ‘2个月‘),
                            (90, ‘3个月‘),
                            (180, ‘6个月‘), (210, ‘12个月‘),
                            (540, ‘18个月‘), (720, ‘24个月‘),
                            )
    valid_period = models.SmallIntegerField(choices=valid_period_choices)
    price = models.FloatField()



class Course(models.Model):
    attachment_path = models.CharField(max_length=128,     
    verbose_name="课件路径", blank=True, null=True)
    status_choices = ((0, ‘上线‘), (1, ‘下线‘), (2, ‘预上线‘))
    status = models.SmallIntegerField(choices=status_choices, 
    default=0)
    template_id = models.SmallIntegerField("前端模板id", 
    default=1)
    coupon = GenericRelation("Coupon")
    # 用于GenericForeignKey反向查询，不会生成表字段，切勿删除
    price_policy = GenericRelation("PricePolicy")

course_obj=models.Course.object.filter(id=1)
price_list=course_obj.price_policy.all()  #获取与之关联的price_policy的所有对象

for price in price_list:     #获取所有字段,和操作其他orm一样.
    print(price.valid_period)
    print(price.price)