第一个Django App（二）
Database setup 数据库安装
1、mysite/settings.py中，Django 2.0默认配置数据库为sqlite3.
# Database
# https://docs.djangoproject.com/en/2.0/ref/settings/#databases
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
}
}
2、mysite/settings.py中，设置TIME_ZONE.
TIME_ZONE = 'UTC'
3、INSTATLLED_APPS保存在该Django例子中所有Django应用的名字。APPS可在多个项目中使用，你可以打包和分发这些应用到其他项目中。
# Application definition
INSTALLED_APPS = [
'django.contrib.admin', //admin站点，你将马上使用的。
'django.contrib.auth', //身份验证系统
'django.contrib.contenttypes',//内容类型框架
'django.contrib.sessions', //session（会话）框架
'django.contrib.messages', //消息框架
'django.contrib.staticfiles', //管理静态文件的框架
]
生成数据库表
python manage.py migrate
migrate命令查找INSTALLED_APPS设置，并根据mysite的数据库设置（mysite/settings.py中）生成任意必要的数据库表以及跟着APP一起迁移数据库。
python3中如何命令行方式看sqlite3数据库？（待学习补充）
migrate命令仅为mysite/settings.py中INSTALLED_APPS有的apps做迁移。
Creating models 创建模型
创建模型，数据库分层，附加的元数据
在简单的poll app中，创建两个模型：Question 和 Choice。
Question有一个question和一个发布日期。
Choice有两个域：选择的文本和计票结果。
每一个Choice域一个Question关联。
polls/models.py
from django.db import models
# Create your models here.
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
class Choice(models.Model):
question = models.ForeignKey(Question,
on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
Activating models 激活模式
给这个app生成数据库模式（CREATE TABLE声明）
为Question和Choice对象生成一个Python可访问的API
但首先我们需要告诉项目polls app安装了。
要在project中包含app，需要在INSTALL_APPS设置中为他的配置类增加引用。PollsConfig类在polls/apps.py文件中。其.路径是‘polls.apps.PollsConfig’.编辑mysite/settings.py文件并增加这个.路径到INSTALLED_APPS配置中，如下：
mysite/settings.py
INSTALLED_APPS = [
'polls.apps.PollsConfig'，
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
]
这样，Django知道包含polls app。下面运行另一个命令：
python manage.py makemigrations polls
root@imhqq-Lenovo-H5050:/home/imhqq/share/django_dev/mysite# python manage.py makemigrations polls
Migrations for 'polls':
polls/migrations/0001_initial.py
- Create model Choice
- Create model Question
- Add field question to choice
通过运行makemigrations，将告诉Django你已经对模式做了一些改动（本例中，生成一个新的模式），这样将改动保存为一个migration（迁移）。
迁移描述的是Django如何保存对模式的改动，迁移仅仅是磁盘上的文件。
polls/migrations/0001_initial.py
# Generated by Django 2.0 on 2017-12-30 06:42
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
initial = True
dependencies = [
]
operations = [
migrations.CreateModel(
name='Choice',
fields=[
('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
('choice_text', models.CharField(max_length=200)),
('votes', models.IntegerField(default=0)),
],
),
migrations.CreateModel(
name='Question',
fields=[
('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
('question_text', models.CharField(max_length=200)),
('pub_date', models.DateTimeField(verbose_name='date published')),
],
),
migrations.AddField(
model_name='choice',
name='question',
field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='polls.Question'),
),
]
迁移设计成人可编辑方式，万一想要手动轻微调整Django是如何改变事情的。
migrate命令用于运行迁移及自动管理数据库架构。
sqlmigrate命令输入需要迁移的名字，返回SQL。
python manage.py sqlmigrate polls 0001
root@imhqq-Lenovo-H5050:/home/imhqq/share/django_dev/mysite# python manage.py sqlmigrate polls 0001
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" ("question_id", "id", "choice_text", "votes") SELECT NULL, "id", "choice_text", "votes" FROM "polls_choice__old";
DROP TABLE "polls_choice__old";
CREATE INDEX "polls_choice_question_id_c5b4b260" ON "polls_choice" ("question_id");
COMMIT;
表名通过结合app（polls)名字与模式-question和choice的低阶名称产生。（可重载）
Primary keys(IDs)自动添加（可重载）。
Django附加“_id”到foreign key域名中（可重载）。
sqlmigration命令不会实际在你的数据库运行迁移，仅仅将此打印到屏幕上。
也可运行python manage.py check.
再次运行migrate，在数据库中生成那些模式表。
root@imhqq-Lenovo-H5050:/home/imhqq/share/django_dev/mysite# python manage.py check
System check identified no issues (0 silenced).
三步阐述模式改变：
1、在models.py中改变模式；
2、运行python manage.py makemigrations来为这些改变生成迁移；
3、运行python manage.py migrate来应用这些改变到数据库。
Playing with the API （玩转API）
绕过manage.py
进入python shell：
python manage.py shell或者输入python
root@imhqq-Lenovo-H5050:/home/imhqq/share/django_dev/mysite# python
Python 3.5.2 (default, Nov 17 2016, 17:05:23)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import django
>>> django.setup()
Traceback (most recent call last):
File "
File "/usr/local/lib/python3.5/dist-packages/django/__init__.py", line 19, in setup
configure_logging(settings.LOGGING_CONFIG, settings.LOGGING)
File "/usr/local/lib/python3.5/dist-packages/django/conf/__init__.py", line 56, in __getattr__
self._setup(name)
File "/usr/local/lib/python3.5/dist-packages/django/conf/__init__.py", line 41, in _setup
% (desc, ENVIRONMENT_VARIABLE))
django.core.exceptions.ImproperlyConfigured: Requested setting LOGGING_CONFIG, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.
>>>
编辑Question模式（在polls/models.py文件中），为Question和Choice增加__str__()方法。
polls/models.py
import datetime
from django.db import models
from django.utils import timezone
# Create your models here.
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
def __str__(self):
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):
question = models.ForeignKey(Question,
on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
def __str__(self):
return self.choice_text
给样式添加__str__()方法很重要，不仅处理交互式提示式时自己方便，也
由于对象的表示应用贯穿于Django自动生成的admin.
Django Admin介绍
1、创建一个admin user
root@imhqq-Lenovo-H5050:/home/imhqq/share/django_dev/mysite# python manage.py createsuperuser
Username (leave blank to use 'root'): root
Email address: [email protected]
Password:
Password (again):
This password is too short. It must contain at least 8 characters.
Password:
Password (again):
Superuser created successfully.
2、启动开发服务器
web浏览器中输入
http://127.0.0.1:8000/admin/.
root@imhqq-Lenovo-H5050:/home/imhqq/share/django_dev/mysite# python manage.py runserver
Performing system checks...
System check identified no issues (0 silenced).
December 30, 2017 - 12:55:15
Django version 2.0, using settings 'mysite.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
[30/Dec/2017 12:55:18] "GET /polls/ HTTP/1.1" 200 40
[30/Dec/2017 12:55:19] "GET /polls/ HTTP/1.1" 200 40
Not Found: /
[30/Dec/2017 12:55:27] "GET / HTTP/1.1" 404 2027
[30/Dec/2017 12:55:36] "GET /admin/ HTTP/1.1" 302 0
[30/Dec/2017 12:55:36] "GET /admin/login/?next=/admin/ HTTP/1.1" 200 1855
[30/Dec/2017 12:55:36] "GET /static/admin/css/login.css HTTP/1.1" 304 0
[30/Dec/2017 12:55:36] "GET /static/admin/css/responsive.css HTTP/1.1" 304 0
[30/Dec/2017 12:55:36] "GET /static/admin/css/base.css HTTP/1.1" 304 0
[30/Dec/2017 12:55:36] "GET /static/admin/css/fonts.css HTTP/1.1" 304 0
[30/Dec/2017 12:55:36] "GET /static/admin/fonts/Roboto-Regular-webfont.woff HTTP/1.1" 304 0
[30/Dec/2017 12:55:36] "GET /static/admin/fonts/Roboto-Light-webfont.woff HTTP/1.1" 304 0
[30/Dec/2017 12:55:43] "POST /admin/login/?next=/admin/ HTTP/1.1" 302 0
[30/Dec/2017 12:55:43] "GET /admin/ HTTP/1.1" 200 2983
[30/Dec/2017 12:55:43] "GET /static/admin/css/dashboard.css HTTP/1.1" 200 412
[30/Dec/2017 12:55:43] "GET /static/admin/img/icon-addlink.svg HTTP/1.1" 200 331
[30/Dec/2017 12:55:43] "GET /static/admin/img/icon-changelink.svg HTTP/1.1" 200 380
[30/Dec/2017 12:55:43] "GET /static/admin/fonts/Roboto-Bold-webfont.woff HTTP/1.1" 304 0
[30/Dec/2017 12:55:50] "GET /admin/auth/group/ HTTP/1.1" 200 3583
[30/Dec/2017 12:55:50] "GET /static/admin/css/changelists.css HTTP/1.1" 200 6170
[30/Dec/2017 12:55:50] "GET /static/admin/js/core.js HTTP/1.1" 200 7134
[30/Dec/2017 12:55:50] "GET /static/admin/js/jquery.init.js HTTP/1.1" 200 363
[30/Dec/2017 12:55:50] "GET /static/admin/js/admin/RelatedObjectLookups.js HTTP/1.1" 200 6897
[30/Dec/2017 12:55:50] "GET /static/admin/js/actions.js HTTP/1.1" 200 6502
[30/Dec/2017 12:55:50] "GET /static/admin/js/prepopulate.js HTTP/1.1" 200 1538
[30/Dec/2017 12:55:50] "GET /admin/jsi18n/ HTTP/1.1" 200 3185
[30/Dec/2017 12:55:50] "GET /static/admin/js/urlify.js HTTP/1.1" 200 8729
[30/Dec/2017 12:55:50] "GET /static/admin/js/vendor/jquery/jquery.js HTTP/1.1" 200 258648
[30/Dec/2017 12:55:50] "GET /static/admin/js/vendor/xregexp/xregexp.js HTTP/1.1" 200 128820
[30/Dec/2017 12:55:50] "GET /static/admin/img/search.svg HTTP/1.1" 200 458
[30/Dec/2017 12:55:50] "GET /static/admin/img/tooltag-add.svg HTTP/1.1" 200 331
[30/Dec/2017 12:55:54] "GET /admin/ HTTP/1.1" 200 2983
3、让admin中的poll app可修改
就做一件事：告诉admin，Question对象有一个admin接口。
polls/admin.py文件修改：
from django.contrib import admin
# Register your models here.
from .models import Question
admin.site.register(Question)
4、Explore the free admin functionally