@receiver(pre_delete, sender=depto)
def delete_depto(sender, instance=None, created=False, **kwargs):
print(instance)
ele=instance.children.all()
for new_ele in ele:
new_ele.parent=instance.parent
new_ele.save()

class depto(models.Model):
name = models.CharField(max_length=50, unique=True,verbose_name=‘部门名称’)
parent = models.ForeignKey(“self”,null=True, blank=True, related_name=‘children’,on_delete=models.SET_NULL)
created_date = models.DateField()
modify_date = models.DateField()

class Meta:
    verbose_name = "部门信息"
    verbose_name_plural = verbose_name

def __str__(self):
    return self.name

如上代码，通过信号量，在删除过程中做一些操作，通过跟踪，代码执行到 new_ele.save()的时候，new_ele.parent已经更新。但程序执行完毕后，去数据库查看，parent的值为NULL 不明所以，望指教