上一篇：老菜鸟学习 Django (一)

三个教程实例

1.创建应用程序 poll

python manage.py startapp polls

这将创建一个目录 polls，其布局如下所示：

polls/
    __init__.py
    admin.py
    apps.py
    migrations/
        __init__.py
    models.py
    tests.py
    views.py

在 views.py 编辑你的第一个视图

from django.shortcuts import render

# Create your views here.

from django import HttpResponse


def index(request):
    return HttpResponse("Hello,world.You're at the polls index。")

polls 新建 urls.py

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

mysite 修改 urls.py

from django.urls import include, path
from django.contrib import admin

urlpatterns = [
    path('polls/', include('polls.urls')),
    path('admin/', admin.site.urls),
]

运行

python manage.py runserver 8001

打开链接http://localhost:8001/polls/，查看页面显示，看到文本 Hello,world.You're at the polls index。

2.创建模型，设置数据库，并介绍 Django 自动生成的 admin 站点

mysite 配置 settings.py

# Application definition

INSTALLED_APPS = [
    # 管理网站
    'django.contrib.admin',
    # 一个认证系统
    'django.contrib.auth',
    # 内容类型的框架
    'django.contrib.contenttypes',
    # 会话框架
    'django.contrib.sessions',
    # 消息传递框架
    'django.contrib.messages',
    # 一个管理静态文件的框架
    'django.contrib.staticfiles',
]

# 默认使用SQLite数据库
DATABASES = {
    'default': {
        # ENGINE包括:'django.db.backends.sqlite3'，'django.db.backends.postgresql'，
        #           'django.db.backends.mysql'，'django.db.backends.oracle'
        'ENGINE': 'django.db.backends.sqlite3',
        # NAME:数据库的名称
        # 如果你不使用SQLite作为数据库，额外的设置，例如 USER，PASSWORD和HOST必须加入
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}

# 设置时区，可以选择'Asia/Shanghai'或者'Asia/Chengdu'
TIME_ZONE = 'Asia/Shanghai'

创建表格

python manage.py migrate

polls 编辑 models.py

from django.db import models
# Create your models here.
class Question(models.Model):
    # 创建Question类，类里有一个question_text，和一个pub_date
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')
class Choice(models.Model):
    # 创建Choice类，类里有一个choice_text，和一个votes
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

mysite 修改 settings.py

# Application definition
INSTALLED_APPS = [
    # 引用polls的配置类PollsConfig，它包含在polls/apps中
    'polls.apps.PollsConfig',
    # 管理网站
    'django.contrib.admin',
    # 一个认证系统
    'django.contrib.auth',
    # 内容类型的框架
    'django.contrib.contenttypes',
    # 会话框架
    'django.contrib.sessions',
    # 消息传递框架
    'django.contrib.messages',
    # 一个管理静态文件的框架
    'django.contrib.staticfiles',
]

运行 makemigrations，您告诉 Django 您已经对模型进行了一些更改，并更改存储为迁移

python manage.py makemigrations polls

结果如下

Migrations for 'polls':
  polls/migrations/0001_initial.py:
    - Create model Choice
    - Create model Question
    - Add field question to choice

运行迁移并自动管理你的数据库模式

python manage.py sqlmigrate polls 0001

结果如下

BEGIN;
--
-- Create model Choice
--
CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL);
--
-- Create model Question
--
CREATE TABLE "polls_question" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "question_text" varchar(200) NOT NULL, "pub_date" datetime NOT NULL);
--
-- Add field question to choice
--
ALTER TABLE "polls_choice" RENAME TO "polls_choice__old";
CREATE TABLE "polls_choice" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL, "question_id" integer NOT NULL REFERENCES "polls_question" ("id") DEFERRABLE INITIALLY DEFERRED);
INSERT INTO "polls_choice" ("id", "choice_text", "votes", "question_id") SELECT "id", "choice_text", "votes", NULL FROM "polls_choice__old";
DROP TABLE "polls_choice__old";
CREATE INDEX "polls_choice_question_id_c5b4b260" ON "polls_choice" ("question_id");
COMMIT;

运行下列命令，检查是否有问题

python manage.py check

再次运行 migrate，创建模型表

python manage.py migrate

结果如下

Operations to perform:
  Apply all migrations: admin, auth, contenttypes, polls, sessions
Running migrations:
  Applying polls.0001_initial... OK

polls 修改 model.py

from django.db import models
import datetime
from django.utils import timezone
# Create your models here.
class Question(models.Model):
    # 创建Question类，类里有一个question_text，和一个pub_date
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')
    def __str__(self):
        # 增加一个__str__方法，用处：一、方便处理交互提示；二：在Django的自动生成的admin中使用对象的表示
        return self.question_text
    def was_published_recently(self):
        # 增加自定义方法
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)
class Choice(models.Model):
    # 创建Choice类，类里有一个choice_text，和一个votes
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)
    def __str__(self):
        # 增加一个__str__方法
        return self.choice_text

创建管理员用户

python manage.py createsuperuser

输入用户名并回车

Username: admin

输入电子邮件地址并回车

Email address: admin@example.com

输入密码并回车，再次输入密码并回车，提示成功

Password: 123456abAB
Password (again): 123456abAB
Superuser created successfully.

运行命令，启动服务器

python manage.py runserver 8001

打开链接http://localhost:8001/admin/，进入登陆页，输入账号密码登陆

如果提示端口被占用
lsof -i tcp:port (port 替换成端口号，比如 8001)
找到占用端口的 pid
kill pid(pid 替换成占用端口的 pid 号)

polls 编辑 admin.py，增加 Question，显示在 admin 页面上

from django.contrib import admin
from .models import Question
# Register your models here.
admin.site.register(Question)

3.