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 models

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)

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.py
2017/06/17  20:17               454 0002_choice_test.py
2017/06/17  20:17               401 0003_remove_choice_test.py
2017/06/17  20:17               447 0004_auto_20170617_1756.py
2017/06/17  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

Created with Raphaël 2.1.0编辑或修改models.py文件makemigrations appmigrate ?预览yesno

编辑或修改polls/models.py文件

将models.py格式化

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.id
1

# Access model field values via Python attributes.
>>> q.question_text
"What's new?"
>>> q.pub_date
datetime.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 models

class Question(models.Model):
# ...
def __str__(self):
return self.question_text

class Choice(models.Model):
# ...
def __str__(self):
return self.choice.text

编辑polls/models.py，add a custom method

import datetime

from django.db import models
from django.utils import timezone

class 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,
b1a9
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 admin

from .models import Question

admin.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。