Django框架详览：从入门到核心功能

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Django框架文档是关于这个流行的Python Web开发框架的详尽指南，由Django Software Foundation维护。该文档在2015年4月21日更新至版本1.8.1.dev20150421155736，主要涵盖了以下几个核心主题： 1. **文档概述**： - 获取帮助：文档提供了入门指南和问题解答路径，帮助用户解决开发过程中的疑问。 - **基础结构**： - 模型层：介绍如何定义数据模型，包括模型类、字段和关系管理。 - 视图层：讲解如何创建处理HTTP请求的视图函数，以及与模板和后端逻辑交互。 - 模板层：详细解释了如何使用Django的模板系统来渲染HTML页面。 - 表单：展示了如何设计表单，验证用户输入和与视图进行数据交互。 - **开发流程**：涉及开发环境设置、单元测试和部署等方面。 2. **深入使用**： - 管理员界面：介绍如何创建和管理后台应用程序管理工具。 - 安全性：讨论了认证、授权和安全配置，确保应用的安全性。 - 国际化与本地化：支持多语言功能，以及如何处理不同地区的文化需求。 - 性能优化：提供性能调优技巧和最佳实践。 - Python兼容性：确保Django与不同Python版本的兼容性。 - 地理框架集成：如果需要地理位置相关的功能，这部分会有指导。 - 其他核心功能：列举了框架内其他实用功能，如中间件、URL路由等。 - Django开源项目：了解项目的背景、贡献者和社区支持。 3. **快速入门**： - Django简介：为初次接触Django的人提供了一个概览。 - 快速安装指南：指导用户如何下载和安装Django。 - 编写第一个Django应用：通过系列步骤，逐步构建一个完整的Web应用实例。 - 进阶教程：学习如何编写可重用的应用组件，提高开发效率。 - 接下来的阅读建议：推荐进一步学习的章节和资源。 - 编写Django补丁：介绍如何参与到框架的改进工作中。 Django框架文档是一份全面且实用的指南，适合从初学者到高级开发者，无论是快速上手还是深入学习，都能在其中找到所需的信息。通过掌握这些内容，开发者可以有效地利用Django进行高效、安全的Web应用程序开发。

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The code above maps URLs, as simple regular expressions, to the location of Python callback functions (“views”).

The regular expressions use parenthesis to “capture” values from the URLs. When a user requests a page, Django runs

through each pattern, in order, and stops at the ﬁrst one that matches the requested URL. (If none of them matches,

Django calls a special-case 404 view.) This is blazingly fast, because the regular expressions are compiled at load

time.

Once one of the regexes matches, Django imports and calls the given view, which is a simple Python function. Each

view gets passed a request object – which contains request metadata – and the values captured in the regex.

For example, if a user requested the URL “/articles/2005/05/39323/”, Django would call the function

news.views.article_detail(request, ’2005’, ’05’, ’39323’).

2.1.6 Write your views

Each view is responsible for doing one of two things: Returning an HttpResponse object containing the content

for the requested page, or raising an exception such as Http404. The rest is up to you.

Generally, a view retrieves data according to the parameters, loads a template and renders the template with the

retrieved data. Here’s an example view for year_archive from above: from django.shortcuts import render

from .models import Article

def year_archive(request, year): a_list = Article.objects.ﬁlter(pub_date__year=year) context =

{‘year’: year, ‘article_list’: a_list} return render(request, ‘news/year_archive.html’, context)

mysite/news/views.py

This example uses Django’s template system, which has several powerful features but strives to stay simple enough

for non-programmers to use.

2.1.7 Design your templates

The code above loads the news/year_archive.html template.

Django has a template search path, which allows you to minimize redundancy among templates. In your Django

settings, you specify a list of directories to check for templates with DIRS. If a template doesn’t exist in the ﬁrst

directory, it checks the second, and so on.

Let’s say the news/year_archive.html template was found. Here’s what that might look like: {% extends

“base.html” %}

{% block title %}Articles for {{ year }}{% endblock %}

{% block content %} <h1>Articles for {{ year }}</h1>

{% for article in article_list %} <p>{{ article.headline }}</p> <p>By {{ article.reporter.full_name

}}</p> <p>Published {{ article.pub_date|date:”F j, Y” }}</p> {% endfor %} {% endblock %}

mysite/news/templates/news/year

𝑎

𝑟𝑐ℎ𝑖𝑣𝑒.ℎ𝑡𝑚𝑙

Variables are surrounded by double-curly braces. {{ article.headline }} means “Output the value of the

article’s headline attribute.” But dots aren’t used only for attribute lookup. They also can do dictionary-key lookup,

index lookup and function calls.

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Note {{ article.pub_date|date:"F j, Y" }} uses a Unix-style “pipe” (the “|” character). This is called

a template ﬁlter, and it’s a way to ﬁlter the value of a variable. In this case, the date ﬁlter formats a Python datetime

object in the given format (as found in PHP’s date function).

You can chain together as many ﬁlters as you’d like. You can write custom template ﬁlters. You can write custom

template tags, which run custom Python code behind the scenes.

Finally, Django uses the concept of “template inheritance”. That’s what the {% extends "base.html" %}

does. It means “First load the template called ‘base’, which has deﬁned a bunch of blocks, and ﬁll the blocks with

the following blocks.” In short, that lets you dramatically cut down on redundancy in templates: each template has to

deﬁne only what’s unique to that template.

Here’s what the “base.html” template, including the use of static ﬁles, might look like: {% load static-

ﬁles %} <html> <head> <title>{% block title %}{% endblock %}</title> </head> <body> <img src=”{%

static “images/sitelogo.png” %}” alt=”Logo” /> {% block content %}{% endblock %} </body> </html>

mysite/templates/base.html

Simplistically, it deﬁnes the look-and-feel of the site (with the site’s logo), and provides “holes” for child templates to

ﬁll. This makes a site redesign as easy as changing a single ﬁle – the base template.

It also lets you create multiple versions of a site, with different base templates, while reusing child templates. Django’s

creators have used this technique to create strikingly different mobile versions of sites – simply by creating a new base

template.

Note that you don’t have to use Django’s template system if you prefer another system. While Django’s template

system is particularly well-integrated with Django’s model layer, nothing forces you to use it. For that matter, you

don’t have to use Django’s database API, either. You can use another database abstraction layer, you can read XML

ﬁles, you can read ﬁles off disk, or anything you want. Each piece of Django – models, views, templates – is decoupled

from the next.

2.1.8 This is just the surface

This has been only a quick overview of Django’s functionality. Some more useful features:

• A caching framework that integrates with memcached or other backends.

• A syndication framework that makes creating RSS and Atom feeds as easy as writing a small Python class.

• More sexy automatically-generated admin features – this overview barely scratched the surface.

The next obvious steps are for you to download Django, read the tutorial and join the community. Thanks for your

interest!

2.2 Quick install guide

Before you can use Django, you’ll need to get it installed. We have a complete installation guide that covers all

the possibilities; this guide will guide you to a simple, minimal installation that’ll work while you walk through the

introduction.

2.2.1 Install Python

Being a Python Web framework, Django requires Python. It works with Python 2.7, 3.2, 3.3, or 3.4. All these versions

of Python include a lightweight database called SQLite so you won’t need to set up a database just yet.

2.2. Quick install guide 11

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Get the latest version of Python at https://www.python.org/download/ or with your operating system’s package man-

ager.

Django on Jython

If you use Jython (a Python implementation for the Java platform), you’ll need to follow a few additional steps. See

Running Django on Jython for details.

You can verify that Python is installed by typing python from your shell; you should see something like:

Python 3.3.3 (default, Nov 26 2013, 13:33:18)

[GCC 4.8.2] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>>

2.2.2 Set up a database

This step is only necessary if you’d like to work with a “large” database engine like PostgreSQL, MySQL, or Oracle.

To install such a database, consult the database installation information.

2.2.3 Remove any old versions of Django

If you are upgrading your installation of Django from a previous version, you will need to uninstall the old Django

version before installing the new version.

2.2.4 Install Django

You’ve got three easy options to install Django:

• Install a version of Django provided by your operating system distribution. This is the quickest option for those

who have operating systems that distribute Django.

• Install an ofﬁcial release. This is the best approach for users who want a stable version number and aren’t

concerned about running a slightly older version of Django.

• Install the latest development version. This is best for users who want the latest-and-greatest features and aren’t

afraid of running brand-new code.

Always refer to the documentation that corresponds to the version of Django you’re using!

If you do either of the ﬁrst two steps, keep an eye out for parts of the documentation marked new in development

version. That phrase ﬂags features that are only available in development versions of Django, and they likely won’t

work with an ofﬁcial release.

2.2.5 Verifying

To verify that Django can be seen by Python, type python from your shell. Then at the Python prompt, try to import

Django:

>>> import django

>>> print(django.get_version())

1.8

You may have another version of Django installed.

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2.2.6 That’s it!

That’s it – you can now move onto the tutorial.

2.3 Writing your ﬁrst Django app, part 1

Let’s learn by example.

Throughout this tutorial, we’ll walk you through the creation of a basic poll application.

It’ll consist of two parts:

• A public site that lets people view polls and vote in them.

• An admin site that lets you add, change and delete polls.

We’ll assume you have Django installed already. You can tell Django is installed and which version by running the

following command:

$ python -c "import django; print(django.get_version())"

If Django is installed, you should see the version of your installation. If it isn’t, you’ll get an error telling “No module

named django”.

This tutorial is written for Django 1.8 and Python 3.2 or later. If the Django version doesn’t match, you can refer to

the tutorial for your version of Django by using the version switcher at the bottom right corner of this page, or update

Django to the newest version. If you are still using Python 2.7, you will need to adjust the code samples slightly, as

described in comments.

See How to install Django for advice on how to remove older versions of Django and install a newer one.

Where to get help:

If you’re having trouble going through this tutorial, please post a message to django-users or drop by #django on

irc.freenode.net to chat with other Django users who might be able to help.

2.3.1 Creating a project

If this is your ﬁrst time using Django, you’ll have to take care of some initial setup. Namely, you’ll need to auto-

generate some code that establishes a Django project – a collection of settings for an instance of Django, including

database conﬁguration, Django-speciﬁc options and application-speciﬁc settings.

From the command line, cd into a directory where you’d like to store your code, then run the following command:

$ django-admin startproject mysite

This will create a mysite directory in your current directory. If it didn’t work, see Problems running django-admin.

Note: You’ll need to avoid naming projects after built-in Python or Django components. In particular, this means

you should avoid using names like django (which will conﬂict with Django itself) or test (which conﬂicts with a

built-in Python package).

Where should this code live?

If your background is in plain old PHP (with no use of modern frameworks), you’re probably used to putting code

under the Web server’s document root (in a place such as /var/www). With Django, you don’t do that. It’s not a

2.3. Writing your ﬁrst Django app, part 1 13

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good idea to put any of this Python code within your Web server’s document root, because it risks the possibility that

people may be able to view your code over the Web. That’s not good for security.

Put your code in some directory outside of the document root, such as /home/mycode.

Let’s look at what startproject created:

mysite/

manage.py

mysite/

__init__.py

settings.py

urls.py

wsgi.py

These ﬁles are:

• The outer mysite/ root directory is just a container for your project. Its name doesn’t matter to Django; you

can rename it to anything you like.

• manage.py: A command-line utility that lets you interact with this Django project in various ways. You can

read all the details about manage.py in django-admin and manage.py.

• The inner mysite/ directory is the actual Python package for your project. Its name is the Python package

name you’ll need to use to import anything inside it (e.g. mysite.urls).

• mysite/__init__.py: An empty ﬁle that tells Python that this directory should be considered a Python

package. (Read more about packages in the ofﬁcial Python docs if you’re a Python beginner.)

• mysite/settings.py: Settings/conﬁguration for this Django project. Django settings will tell you all

about how settings work.

• mysite/urls.py: The URL declarations for this Django project; a “table of contents” of your Django-

powered site. You can read more about URLs in URL dispatcher.

• mysite/wsgi.py: An entry-point for WSGI-compatible web servers to serve your project. See How to

deploy with WSGI for more details.

Database setup

Now, edit mysite/settings.py. It’s a normal Python module with module-level variables representing Django

settings.

By default, the conﬁguration uses SQLite. If you’re new to databases, or you’re just interested in trying Django, this is

the easiest choice. SQLite is included in Python, so you won’t need to install anything else to support your database.

When starting your ﬁrst real project, however, you may want to use a more robust database like PostgreSQL, to avoid

database-switching headaches down the road.

If you wish to use another database, install the appropriate database bindings, and change the following keys in the

DATABASES ’default’ item to match your database connection settings:

• ENGINE – Either ’django.db.backends.sqlite3’, ’django.db.backends.postgresql_psycopg2’,

’django.db.backends.mysql’, or ’django.db.backends.oracle’. Other backends are also

available.

• NAME – The name of your database. If you’re using SQLite, the database will be a ﬁle on your computer;

in that case, NAME should be the full absolute path, including ﬁlename, of that ﬁle. The default value,

os.path.join(BASE_DIR, ’db.sqlite3’), will store the ﬁle in your project directory.

14 Chapter 2. Getting started

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