model 字段参数 choice

class Banner(NewsBase):
    '''
    轮播图
    '''
    PRI_CHOICES = [     # 优先级的限制选择范围
        (1,'第一级'),
        (2,'第二级'),
        (3,'第三级'),
        (4,'第四级'),
        (5,'第五级'),
        (6,'第六级')
    ]
    image_url = models.CharField(verbose_name='图片url',max_length=200)
    priority = models.IntegerField(verbose_name='优先级',choices=PRI_CHOICES,default=6)   # choices参数,限制输入范围.
    news = models.OneToOneField('news',on_delete=models.CASCADE)

    class Meta:
        ordering = ['priority','-update_time']
        db_table = 'tb_banner'
        verbose_name = '轮播图'
        verbose_name_plural=verbose_name

    def __str__(self):
        return '<轮播图{}>'.format(self.id)

choices   字段选择限制.类型于'枚举'