python之如何根据同一模型中其他字段的值设置django模型字段值

我想分配一个 NullBooleanField 值以始终反对同一模型中的其他字段值，None 除外。从下面的模型中，我想确定 scam 的值是否为 True，whitelist 的值不能也为 True 。但是如果scam是None，whitelist允许也设置为None。预期条件是以下之一:

1. 如果scam为True，则whitelist的允许值为False或None
2. 如果scam为False，则whitelist的允许值为True或None
3. 如果scam为None，whitelist的允许值为True或False 或 None

那么，如何确保scam永远是whitelist的对立面呢？

这是我的类(class)模型:

class ExtendHomepage(models.Model): 
    "extending homepage model to add more field" 
    homepage = models.OneToOneField(Homepage) 
 
    # True if the website is a scam, False if not, None if not sure 
    scam = models.NullBooleanField(blank=True, null=True) 
 
    # True if the webpage is already inspected, False if not  
    inspected = models.BooleanField(default=False) 
 
    # True if the website is already reported, False if not yet  
    reported =  models.NullBooleanField(blank=True, null=True) 
 
    # True if the website response is 200, else it is False 
    access =  models.BooleanField(default=True) 
 
    # True if the web should be whitelist, False if should not, None pending 
    whitelist =  models.NullBooleanField(blank=True, null=True) 

请您参考如下方法:

您可以为这种必要性制作一个属性 getter 和setter，类似于下面的代码:

class ExtendHomepage(models.Model): 
    "extending homepage model to add more field" 
    homepage = models.OneToOneField(Homepage) 
 
    # True if the website is a scam, False if not, None if not sure 
    scam = models.NullBooleanField(blank=True, null=True) 
 
    # True if the webpage is already inspected, False if not  
    inspected = models.BooleanField(default=False) 
 
    # True if the website is already reported, False if not yet  
    reported =  models.NullBooleanField(blank=True, null=True) 
 
    # True if the website response is 200, else it is False 
    access =  models.BooleanField(default=True) 
 
    # True if the web should be whitelist, False if should not, None pending 
 
    __whitelist = models.NullBooleanField(blank=True, null=True) 
 
    @property 
    def whitelist(self): 
        if self.scam is not None and self.scam == self.__whitelist: 
            # this if block is not necessary but for  
            # check if content changed directly in database manager 
            # then assign None value to this attribute 
            self.__whitelist = None 
        return self.__whitelist 
 
    @whitelist.setter 
    def whitelist(self, value): 
        self.__whitelist = value 
        if self.scam is not None and self.scam == self.__whitelist: 
            self.__whitelist = None