Django入门（1）

18.1 建立项目

　　建立项目时，首先要以规范的方式对项目进行描述，再建立虚拟环境，以便在其中创建项目

1.1 制定规范

　　完整的规范详细说明了项目的目标，功能，外观和用户界面。该项目规范如下：

　　我们要编写一个名为‘学习笔记’的web应用程序，让用户能记录感兴趣的主题，并在学习每个主题的过程中添加日志条目。‘学习笔记’的主页对这个网站进行描述，并邀请用户注册或登录。用户登录后，就可以创建新主题、添加新条目以及阅读既有的条目。

1.2 建立虚拟环境

　　使用Django，首先建立一个虚拟环境。这对以后将‘学习笔记’部署到服务器上也是必须的。

1.3 安装 virtualenv

1.4 激活虚拟环境

l@ubuntu:~/Documents/lyb$ source bin/activate   #激活命令
(lyb) l@ubuntu:~/Documents/lyb$　　　　　　　     #激活状态
deactivate　　　　　　　　　　　　　　　　　         #退出激活状态

1.5 安装Django

激活状态下：

pip install Django

1.6 在Django中创建项目

(lyb) l@ubuntu:~/Documents$ django-admin.py startproject learning_log .
(lyb) l@ubuntu:~/Documents$ ls
learning_log  lyb  manage.py
(lyb) l@ubuntu:~/Documents$ ls learning_log
__init__.py  settings.py  urls.py  wsgi.py
(lyb) l@ubuntu:~/Documents$ 

1.7 创建数据库

(lyb) l@ubuntu:~/Documents$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying sessions.0001_initial... OK
(lyb) l@ubuntu:~/Documents$ ls
db.sqlite3  learning_log  lyb  manage.py

1.8 查看项目

(lyb) l@ubuntu:~/Documents$ python manage.py runserver
Performing system checks...

System check identified no issues (0 silenced).
November 04, 2017 - 16:13:50
Django version 1.11.7, using settings 'learning_log.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

18.2 创建应用程序

 重新打开一个终端：

l@ubuntu:~/Documents$ source lyb/bin/activate
(lyb) l@ubuntu:~/Documents$ python manage.py startapp learning_logs
(lyb) l@ubuntu:~/Documents$ ls
db.sqlite3  learning_log  learning_logs  lyb  manage.py
(lyb) l@ubuntu:~/Documents$ ls learning_logs/
admin.py  apps.py  __init__.py  migrations  models.py  tests.py  views.py
(lyb) l@ubuntu:~/Documents$ 

2.1 定义模型

打开models.py，输入模型：

from django.db import models

# Create your models here.
class Topic(models.Model):
    '''用户学习的主题'''
    text = models.CharField(max_length=200)
    date_added = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        '返回模型的字符串表示
        return self.text    

2.2 激活模型

打开/home/l/Documents/learning_log中的setting.py，在INSTALLED_APPS中添加 ‘learning_logs’

继续命令行：

(lyb) l@ubuntu:~/Documents$ python manage.py makemigrations learning_logs
Migrations for 'learning_logs':
  learning_logs/migrations/0001_initial.py
    - Create model Topic
(lyb) l@ubuntu:~/Documents$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, learning_logs, sessions
Running migrations:
  Applying learning_logs.0001_initial... OK

　　每当需要修改‘学习笔记’管理的数据时，都采取如下三个步骤：修改models.py；对learning_logs调用makemigrations；让Django迁移项目。

2.3 Django管理网站

　　1 创建超级用户

(lyb) l@ubuntu:~/Documents$ python manage.py createsuperuser
Username (leave blank to use 'l'): lyb
Email address: 
Password: 
Password (again): 
This password is too short. It must contain at least 8 characters.
Password: 
Password (again): 
Superuser created successfully.

　　2. 向管理网站注册模型

　　打开models.py所在目录中的admin.py，输入：

from django.contrib import admin

# Register your models here.
from learning_logs.models import Topic

admin.site.register(Topic)

　　打开浏览器访问http://localhost:8000/admin/，输入超级用户名及密码后你会看到：

 

　　3. 添加主题

2.4 定义模型Entry

models.py

class Entry(models.Model):
    '''学到的有关某个主题的具体知识'''
    topic = models.ForeignKey(Topic)
    text = models.TextField()
    date_added = models.DateTimeField(auto_now_add=True)

    class Meta:
        verbose_name_plural = 'entries'

    def __str__(self):
        '返回模型的字符串表示'
        return self.text[:50] + '...'

2.5 迁移模型Entry

(lyb) l@ubuntu:~/Documents$ python manage.py makemigrations learning_logs
Migrations for 'learning_logs':
  learning_logs/migrations/0002_entry.py
    - Create model Entry
(lyb) l@ubuntu:~/Documents$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, learning_logs, sessions
Running migrations:
  Applying learning_logs.0002_entry... OK

2.6 向管理网站注册Entry

admin.py

from django.contrib import admin

# Register your models here.
from learning_logs.models import Topic,Entry

admin.site.register(Topic)
admin.site.register(Entry)

2.7 Django shell

(lyb) l@ubuntu:~/Documents$ python manage.py shell
Python 3.5.2 (default, Sep 14 2017, 22:51:06) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from learning_logs.models import Topic
>>> Topic.objects.all()
<QuerySet [<Topic: chess>, <Topic: Rock Clibing>]>     # QuerySet 查询集