1. 如何建立一对一的关系模型？ ¶

from django.contrib.auth.models import User
class UserParent(models.Model):
    user = models.OneToOneField(
        User,
        on_delete=models.CASCADE,
        primary_key=True,
    father_name = models.CharField(max_length=100)
    mother_name = models.CharField(max_length=100)
>>> u1 = User.objects.get(first_name='Ritesh', last_name='Deshmukh')
>>> u2 = User.objects.get(first_name='Sohan', last_name='Upadhyay')
>>> p1 = UserParent(user=u1, father_name='Vilasrao Deshmukh', mother_name='Vaishali Deshmukh')
>>> p1.save()
>>> p1.user.first_name
'Ritesh'
>>> p2 = UserParent(user=u2, father_name='Mr R S Upadhyay', mother_name='Mrs S K Upadhyay')
>>> p2.save()
>>> p2.user.last_name
'Upadhyay'
on_delete 方法被用于告诉Django如何处理依赖你删除模型实例的模型实例（如外键关系）。on_delete=models.CASCADE 告诉Django执行级联删除效果，即，继续也把依赖模型删除。
>>> u2.delete()
并将删除 UserParent 的关联记录。