Writing your first Django app, part 2

官方教程-Part2

数据库设置

安装数据库
mysite/settings.py

SQLite

DATABASES = {    'default': {        'ENGINE':'django.db.backends.sqlite3',        'NAME': 'mydatabase',    }}

MySQL/Oracle/PostgreSQL

DATABASES = {    'default': {        'ENGINE': 'django.db.backends.postgresql',        'NAME': 'mydatabase',        'USER': 'mydatabaseuser',        'PASSWORD': 'mypassword',        'HOST': '127.0.0.1',        'PORT': '5432',    }}

安装应用

mysite/settings.py

默认情况下，INSTALLED_APPS包含以下应用程序，所有这些应用程序都与Django一起提供：

• django.contrib.admin - 管理网站。你会很快使用它。
• django.contrib.auth - 认证系统。
• django.contrib.contenttypes - 内容类型的框架。
• django.contrib.sessions - 会话框架
• django.contrib.messages - 消息框架。
• django.contrib.staticfiles - 管理静态文件的框架。

创建数据库

# directory: mysite/manage.py$ python manage.py migrate

创建models

polls/models.py

from django.db import modelsclass 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)

安装应用

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',]

将polls/models.py 中的类转换成统一格式，为生成数据库中的表做准备

polls/models.py -格式化-> polls/migration/number_comment.py

$ python manage.py makemigrations polls

会在polls/migrations/生成如下类似文件

2017/06/17  20:17             1,268 0001_initial.py2017/06/17  20:17               454 0002_choice_test.py2017/06/17  20:17               401 0003_remove_choice_test.py2017/06/17  20:17               447 0004_auto_20170617_1756.py2017/06/17  20:17               447 0005_auto_20170617_1757.py

查看格式化后的文件将运行什么SQL

$ python manage.py sqlmigrate polls 0001

生成的文件，(migrate)运行以在数据库中创建这些模型表：

$ python manage.py migrate

要执行的操作：
应用所有迁移：admin，auth，contenttypes，polls，sessions
运行迁移：
渲染模型状态… DONE
应用polls.0001_initial … OK

1. 编辑或修改polls/models.py文件
2. 将models.py格式化
3. 执行migrate

进入命令行调试

$ python manage.py shell

>>> from polls.models import Question, Choice   # Import the model classes we just wrote.# No questions are in the system yet.>>> Question.objects.all()<QuerySet []># Create a new Question.# Support for time zones is enabled in the default settings file, so# Django expects a datetime with tzinfo for pub_date. Use timezone.now()# instead of datetime.datetime.now() and it will do the right thing.>>> from django.utils import timezone>>> q = Question(question_text="What's new?", pub_date=timezone.now())# Save the object into the database. You have to call save() explicitly.>>> q.save()# Now it has an ID. Note that this might say "1L" instead of "1", depending# on which database you're using. That's no biggie; it just means your# database backend prefers to return integers as Python long integer# objects.>>> q.id1# Access model field values via Python attributes.>>> q.question_text"What's new?">>> q.pub_datedatetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>)# Change values by changing the attributes, then calling save().>>> q.question_text = "What's up?">>> q.save()# objects.all() displays all the questions in the database.>>> Question.objects.all()<QuerySet [<Question: Question object>]>

编辑polls/models.py，add __str__() methods to your models

from django.db import modelsclass Question(models.Model):    # ...    def __str__(self):        return self.question_textclass Choice(models.Model):    # ...    def __str__(self):        return self.choice.text

编辑polls/models.py，add a custom method

import datetimefrom django.db import modelsfrom django.utils import timezoneclass Question(models.Model):    # ...    def was_published_recently(self):        return self.pub_date >= timezome.now() - datetime.timedelta(days=1)

保存这些更改并重新启动一个新的Python交互式shell ：python manage.py shell

>>> from polls.models import Question, Choice# Make sure our __str__() addition worked.>>> Question.objects.all()<QuerySet [<Question: What's up?>]># Django provides a rich database lookup API that's entirely driven by# keyword arguments.>>> Question.objects.filter(id=1)<QuerySet [<Question: What's up?>]>>>> Question.objects.filter(question_text__startswith='What')<QuerySet [<Question: What's up?>]># Get the question that was published this year.>>> from django.utils import timezone>>> current_year = timezone.now().year>>> Question.objects.get(pub_date__year=current_year)<Question: What's up?># Request an ID that doesn't exist, this will raise an exception.>>> Question.objects.get(id=2)Traceback (most recent call last):    ...DoesNotExist: Question matching query does not exist.# Lookup by a primary key is the most common case, so Django provides a# shortcut for primary-key exact lookups.# The following is identical to Question.objects.get(id=1).>>> Question.objects.get(pk=1)<Question: What's up?># Make sure our custom method worked.>>> q = Question.objects.get(pk=1)>>> q.was_published_recently()True# Give the Question a couple of Choices. The create call constructs a new# Choice object, does the INSERT statement, adds the choice to the set# of available choices and returns the new Choice object. Django creates# a set to hold the "other side" of a ForeignKey relation# (e.g. a question's choice) which can be accessed via the API.>>> q = Question.objects.get(pk=1)# Display any choices from the related object set -- none so far.>>> q.choice_set.all()<QuerySet []># Create three choices.>>> q.choice_set.create(choice_text='Not much', votes=0)<Choice: Not much>>>> q.choice_set.create(choice_text='The sky', votes=0)<Choice: The sky>>>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)# Choice objects have API access to their related Question objects.>>> c.question<Question: What's up?># And vice versa: Question objects get access to Choice objects.>>> q.choice_set.all()<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>>>> q.choice_set.count()3# The API automatically follows relationships as far as you need.# Use double underscores to separate relationships.# This works as many levels deep as you want; there's no limit.# Find all Choices for any question whose pub_date is in this year# (reusing the 'current_year' variable we created above).>>> Choice.objects.filter(question__pub_date__year=current_year)<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]># Let's delete one of the choices. Use delete() for that.>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')>>> c.delete()

创建超级管理员

$ python manage.py createsuperuser# 根据提示录入Username|Password

访问 http://localhost:9000/admin/

Make the poll app modifiable in the admin

polls.py/admin.py

from django.contrib import adminfrom .models import Questionadmin.site.register(Question)

重启服务

$ python manage.py runserver

访问 http://localhost:9000/admin/

http://localhost:9000/admin/polls/question/add/
注意事项：

• 表单是从Question模型自动生成的。
• 不同的模型字段类型（DateTimeField， CharField）对应于适当的HTML输入小部件。每种类型的字段知道如何在Django管理员中显示自己。
• 每个都DateTimeField获得免费的JavaScript快捷方式。日期获取“今日”快捷方式和日历弹出窗口，并且时间获取“Now”快捷方式和一个方便的弹出窗口，列出常用的时间。

页面底部提供了几个选项：

• 保存 - 保存更改并返回到此类型对象的更改列表页面。
• 保存并继续编辑 - 保存更改并重新加载此对象的管理页面。
• 保存并添加另一个 - 保存更改并加载此类型对象的新的空白表单。
• 删除 - 显示删除确认页面。