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文件名称：相关的对象-libmodbus源码解析
文件大小：7.37MB
文件格式：PDF
更新时间：2021-06-24 08:00:41
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9.1相关的对象
我们在第 4 章定义了下面几个模型：
from django.db import models
class Publisher(models.Model):
name = models.CharField(max_length=30)
address = models.CharField(max_length=50)
city = models.CharField(max_length=60)
state_province = models.CharField(max_length=30)
country = models.CharField(max_length=50)
website = models.URLField()
def __str__(self):
return self.name
class Author(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=40)
email = models.EmailField()
def __str__(self):
return '%s %s' % (self.first_name, self.last_name)
class Book(models.Model):
title = models.CharField(max_length=100)
authors = models.ManyToManyField(Author)
publisher = models.ForeignKey(Publisher)
publication_date = models.DateField()
def __str__(self):
return self.title
我们知道，访问数据库中某一列很简单，只需访问对象的属性。例如，若想查看 ID 为 50 的图书的书名，可
以这么做：
>>> from mysite.books.models import Book
>>> b = Book.objects.get(id=50)
>>> b.title
'The Django Book'
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