[Dynamic Language] Python Django: 模型使用

Django 模型

//创建App应用程序
python manage.py startapp books

//建立模型

  1 from django.db import models
  2
  3 # Create your models here.
  4
  5 class Publisher(models.Model):
  6     name = models.CharField(max_length=30)
  7     address = models.CharField(max_length=50)
  8     city = models.CharField(max_length=60)
  9     state_province = models.CharField(max_length=30)
 10     country = models.CharField(max_length=50)
 11     website = models.URLField()
 12
 13 class Author(models.Model):
 14     first_name = models.CharField(max_length=100)
 15     last_name = models.CharField(max_length=40)
 16     email = models.EmailField()
 17
 18 class Book(models.Model):
 19     title = models.CharField(max_length=100)
 20     authors = models.ManyToManyField(Author)
 21     publisher = models.ForeignKey(Publisher)
 22     publication_date = models.DateField()

模型安装
修改 settings.py 配置信息

 70 MIDDLEWARE_CLASSES = (
 71 #    'django.middleware.common.CommonMiddleware',
 72 #    'django.contrib.sessions.middleware.SessionMiddleware',
 73 #    'django.middleware.csrf.CsrfViewMiddleware',
 74 #    'django.contrib.auth.middleware.AuthenticationMiddleware',
 75 #    'django.contrib.messages.middleware.MessageMiddleware',
 76 )
 88 INSTALLED_APPS = (
 89 #    'django.contrib.auth',
 90 #    'django.contrib.contenttypes',
 91 #    'django.contrib.sessions',
 92     'django.contrib.sites',
 93 #    'django.contrib.messages',
 94      'mysite.books',
 95     # Uncomment the next line to enable the admin:
 96     # 'django.contrib.admin',
 97 )

//验证模型的有效性

abeen@localhost:~/django_test/mysite$ python manage.py  validate
0 errors found

//打印输出sql语句

abeen@localhost:~/django_test/mysite$ python manage.py sqlall books
BEGIN;
CREATE TABLE `books_publisher` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `name` varchar(30) NOT NULL,
    `address` varchar(50) NOT NULL,
    `city` varchar(60) NOT NULL,
    `state_province` varchar(30) NOT NULL,
    `country` varchar(50) NOT NULL,
    `website` varchar(200) NOT NULL
);
CREATE TABLE `books_author` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `first_name` varchar(100) NOT NULL,
    `last_name` varchar(40) NOT NULL,
    `email` varchar(75) NOT NULL
);
CREATE TABLE `books_book_authors` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `book_id` integer NOT NULL,
    `author_id` integer NOT NULL,
    UNIQUE (`book_id`, `author_id`)
);
ALTER TABLE `books_book_authors` ADD CONSTRAINT `author_id_refs_id_9e7e386` 
FOREIGN KEY (`author_id`) REFERENCES `books_author` (`
CREATE TABLE `books_book` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `title` varchar(100) NOT NULL,
    `publisher_id` integer NOT NULL,
    `publication_date` date NOT NULL
);
ALTER TABLE `books_book` ADD CONSTRAINT `publisher_id_refs_id_c5b274bb` 
FOREIGN KEY (`publisher_id`) REFERENCES `books_publisher`
ALTER TABLE `books_book_authors` ADD CONSTRAINT `book_id_refs_id_cfbcf262` 
FOREIGN KEY (`book_id`) REFERENCES `books_book` (`id`);
CREATE INDEX `books_book_22dd9c39` ON `books_book` (`publisher_id`);
COMMIT;

//同步模型到数据库

abeen@localhost:~/django_test/mysite$ python manage.py  syncdb
Creating table books_publisher
Creating table books_author
Creating table books_book_authors
Creating table books_book
Installing index for books.Book_authors model
Installing index for books.Book model
No fixtures found.

基本数据访问

In [1]: from books.models import Publisher //导入
//创建对象
In [2]: p = Publisher(name='Apress',address='2855,Telegraph Avenue',city='Berkeley',
state_province='CA',country='USA',website='http://www.jinry.com')
//存入数据库
In [3]: p.save()
In [4]: p2 = Publisher(name='Apress',address='2855,Telegraph Avenue',city='Berkeley',
state_province='CA',country='USA',website='http://www.jinry.com')
In [5]: p2.save()
//取信息
In [6]: publisher_list = Publisher.objects.all()
In [7]: publisher_list
Out[7]: [<Publisher: Publisher object>, <Publisher: Publisher object>]
In [8]: type(publisher_list)
Out[8]: <class 'django.db.models.query.QuerySet'>

//创建并直接存入数据库
In [9]: p2 =  Publisher.objects.create(name='Apress',address='2855,Telegraph Avenue',
city='Berkeley',state_province='CA',country='USA',website='http://www.jinry.com')

选择对象集

In [9]: publisher_list = Publisher.objects.all()//取全部
In [10]: publisher_list
Out[10]: [<Publisher: abeen>, <Publisher: shanshan>, <Publisher: Apress>] 

数据过滤

In [16]: publisher = Publisher.objects.filter(name="abeen")
In [17]: publisher
Out[17]: [<Publisher: abeen>]
//sql and


In [21]: publishers = Publisher.objects.filter(name="abeen", city="hai dian") 

In [22]: publishers
Out[22]: [<Publisher: abeen>]
In [23]: publishers = Publisher.objects.filter(name__contains="a") //包含关系
In [25]: publishers
Out[25]: [<Publisher: abeen>, <Publisher: shanshan>]

获取单个对象

In [27]: p = Publisher.objects.get(name="abeen")
In [28]: p
Out[28]: <Publisher: abeen>

注意get在取不到结果或取到多个结果时，会报DoesNotExist错误，程序要自己处理。如：

In [30]: try:
   ....:     p = Publisher.objects.get(name="abeen1")
   ....: except Publisher.DoesNotExist:
   ....:     print "abeen1 is not in "
   ....: else:
   ....:     p
   ....:
   ....:
abeen1 is not in

数据排序

In [39]: Publisher.objects.all()
Out[39]: [<Publisher: abeen>, <Publisher: shanshan>, <Publisher: Apress>,
 <Publisher: binbin>, <Publisher: qiqi>, <Publisher: lanlan>]
In [40]: Publisher.objects.order_by("name") //按name排序
Out[40]: [<Publisher: abeen>, <Publisher: Apress>, <Publisher: binbin>, 
<Publisher: lanlan>, <Publisher: qiqi>, <Publisher: shanshan>]
In [41]: Publisher.objects.order_by("name", "city") //多字段排序
Out[41]: [<Publisher: abeen>, <Publisher: Apress>, <Publisher: binbin>, 
<Publisher: lanlan>, <Publisher: qiqi>, <Publisher: shanshan>]
In [42]: Publisher.objects.order_by("-name") //逆向排序，在前面加一个减号 - 前缀
Out[42]: [<Publisher: shanshan>, <Publisher: qiqi>, <Publisher: lanlan>, 
<Publisher: binbin>, <Publisher: Apress>, <Publisher: abeen>]

如果感觉每次查询都要写order_by啰嗦的话，可以用Meta来设置模型默认的排序字段

  5 class Publisher(models.Model):
  6     name = models.CharField(max_length=30)
  7     address = models.CharField(max_length=50)
  8     city = models.CharField(max_length=60)
  9     state_province = models.CharField(max_length=30)
 10     country = models.CharField(max_length=50)
 11     website = models.URLField()
 12
 13     def __unicode__(self):
 14         return self.name
 15
 16     class Meta:
 17         ordering = ['name']

查询看一下结果默认按name排序了

In [1]: from books.models import Publisher
In [2]: P = Publisher
In [3]: P.objects.all()
Out[3]: [<Publisher: abeen>, <Publisher: Apress>, <Publisher: binbin>, 
<Publisher: lanlan>, <Publisher: qiqi>, <Publisher: shanshan>]

注意可以在任意一个模型类中使用 Meta 类，来设置一些与特定模型相关的选项。
（参考与特定模型相关选项 http://djangobook.py3k.cn/appendixB/）

 

连锁查询

In [5]: p = Publisher.objects.filter(name__contains="a").order_by("name")
In [6]: p
Out[6]: [<Publisher: abeen>, <Publisher: lanlan>, <Publisher: shanshan>]

限制返回的数据

In [7]: Publisher.objects.all()[1] //按索引号取
Out[7]: <Publisher: Apress>
In [8]: Publisher.objects.all()[0:2] //按范围取
Out[8]: [<Publisher: abeen>, <Publisher: Apress>]
In [9]: Publisher.objects.all().order_by("-name")[0:2] //不支持负索引，可以后逆排实现效果
Out[9]: [<Publisher: shanshan>, <Publisher: qiqi>]

更新多个对象

In [11]: p = Publisher.objects.get(name="abeen")
In [12]: p
Out[12]: <Publisher: abeen>
In [13]: p.name="new abeen"
In [14]: p.save() //将所有字段都更新，即使只修改某个字段

先看一下数据库数据

mysql> select * from books_publisher;
+----+-----------+-----------------------+------------+----------------+---------+----------------------+
| id | name      | address               | city       | state_province | country | website              |
+----+-----------+-----------------------+------------+----------------+---------+----------------------+
|  1 | new abeen | 2855,Telegraph Avenue | hai dian   | CA             | USA     | http://www.jinry.com |
|  2 | shanshan  | 2855,Telegraph Avenue | feng tai   | CA             | USA     | http://www.jinry.com |
|  3 | Apress    | 2855,Telegraph Avenue | Berkeley   | CA             | USA     | http://www.jinry.com |
|  4 | binbin    |                       | shou guang |                |         |                      |
|  5 | qiqi      |                       | shou guang |                |         |                      |
|  6 | lanlan    |                       | shou guang |                |         |                      |
+----+-----------+-----------------------+------------+----------------+---------+----------------------+
In [16]: Publisher.objects.filter(id="1").update(name="abeen")
Out[16]: 1L
In [17]: Publisher.objects.all().update(website="http://www.jinry.com")
Out[17]: 6L

数据已修改

mysql> select * from books_publisher;
+----+----------+-----------------------+------------+----------------+---------+----------------------+
| id | name     | address               | city       | state_province | country | website              |
+----+----------+-----------------------+------------+----------------+---------+----------------------+
|  1 | abeen    | 2855,Telegraph Avenue | hai dian   | CA             | USA     | http://www.jinry.com |
|  2 | shanshan | 2855,Telegraph Avenue | feng tai   | CA             | USA     | http://www.jinry.com |
|  3 | Apress   | 2855,Telegraph Avenue | Berkeley   | CA             | USA     | http://www.jinry.com |
|  4 | binbin   |                       | shou guang |                |         | http://www.jinry.com |
|  5 | qiqi     |                       | shou guang |                |         | http://www.jinry.com |
|  6 | lanlan   |                       | shou guang |                |         | http://www.jinry.com |
+----+----------+-----------------------+------------+----------------+---------+----------------------+

删除对象

In [18]: Publisher.objects.filter(name="lanlan").delete()
In [19]: p = Publisher.objects.get(name="binbin")
In [20]: p.delete()

//删除表数据时要注意，显示调用all(),否则会出如下错误

In [21]: Publisher.objects.delete()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/home/abeen/django_test/mysite/<ipython console> in <module>()
AttributeError: 'Manager' object has no attribute 'delete'

//删除表内全部数据
In [22]: Publisher.objects.all().delete()