对于某个字段可以适用枚举类。写法是：

charfield(choices=( (1,"free"),(2,"basic"),(3,"premium")    ), default = 0)

1 to 1关系的外键用

teacher_id = models.OneToOneField()

django做migration时会自动生成多对多的关系表

4-2笔记

模型类开发实例

f"{self.get_type_display()}-{self.title}"

等效于  "{}-{}".format(self.get_type_display(),self.title)

created_at =  models.DateTimeField (auto_now_add=True ,verbose_name ='创建时间")

updated_at =models.DateTimeField(auto_now, verbose_name ='更新时间")

auto_now_add = True