Django 3.0.2.dev 文档：入门与核心技术指南

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"Django.pdf，这是Django软件基金会发布的Django 3.0.2.dev版官方文档。文档旨在帮助读者深入理解Django的设计理念和理论，即使遇到不熟悉的英文词汇，通过查阅字典也能逐步掌握。内容涵盖Django的各个层面，包括模型层、视图层、模板层、表单处理、开发流程、管理界面、安全性、国际化与本地化、性能优化、地理框架以及常用Web应用工具等。此外，还提供了快速安装指南和详尽的新手入门教程，帮助开发者从零开始构建Django应用。" Django是基于Python的Web框架，它强调了可重用性和“干”(Don't Repeat Yourself)的原则。在Django 3.0.2.dev的文档中，首先介绍了如何获取帮助和文档的组织结构，这对于初学者来说是非常重要的，因为它能帮助读者快速定位所需的信息。 1. 模型层(Model Layer): Django的核心之一是它的ORM(Object-Relational Mapping)，允许开发者使用Python类来定义数据库模式。模型层是应用程序与数据库交互的主要方式，包含了数据字段、关系和业务逻辑。 2. 视图层(View Layer): 视图负责处理HTTP请求并返回HTTP响应。它们通常包含业务逻辑，根据用户请求返回适当的数据或执行操作。 3. 模板层(Template Layer): 模板系统是用于呈现HTML和其他类型的文件，它允许开发者以声明式的方式描述动态内容。Django的模板语言支持变量插入、控制流和过滤器。 4. 表单(Form): Django提供了强大的表单处理功能，包括自动生成HTML表单、验证用户输入和处理表单数据。 5. 开发过程(Development Process): 文档详细描述了Django的开发流程，包括设置开发环境、调试、测试和部署等步骤。 6. 管理界面(Admin): Django的内置管理界面是一个强大工具，可以帮助开发者快速创建后台管理系统，用于编辑和管理网站数据。 7. 安全性(Security): 文档会涵盖各种安全话题，如防止SQL注入、跨站脚本攻击(XSS)和跨站请求伪造(CSRF)等。 8. 国际化和本地化(Internationalization and Localization): Django支持多语言，文档将解释如何实现应用的国际化和本地化。 9. 性能和优化(Performance and Optimization): 提供了提高Django应用性能的技巧和最佳实践。 10. 地理框架(Geographic Framework): Django包含对地理数据的支持，如GIS(地理信息系统)功能。 11. 常用Web应用工具(Common Web Application Tools): 文档可能包含如缓存、中间件、日志记录和电子邮件发送等常见Web开发功能。 12. 其他核心功能(Other Core Functionalities): 这部分可能会涵盖Django中未在其他章节详细介绍的功能。 13. 开源项目(The Django Open-Source Project): 介绍了Django的社区、贡献方式以及如何参与开源项目。文档还包括快速入门指南，从零开始引导读者创建第一个Django应用，分为多个部分，逐步介绍每个关键概念。最后，还提供了一个关于如何为Django编写补丁的高级教程，鼓励读者参与到Django的开发中去。这份文档是学习和深入理解Django的宝贵资源。

Django Documentation, Release 3.0.2.dev

Listing 3: mysite/news/admin.py

from django.contrib import admin

from . import models

admin.site.register(models.Article)

The philosophy here is that your site is edited by a staff, or a client, or maybe just you – and you don’t want to have to

deal with creating backend interfaces only to manage content.

One typical workﬂow in creating Django apps is to create models and get the admin sites up and running as fast as

possible, so your staff (or clients) can start populating data. Then, develop the way data is presented to the public.

2.1.5 Design your URLs

A clean, elegant URL scheme is an important detail in a high-quality Web application. Django encourages beautiful

URL design and doesn’t put any cruft in URLs, like .php or .asp.

To design URLs for an app, you create a Python module called a URLconf . A table of contents for your app, it contains

a mapping between URL patterns and Python callback functions. URLconfs also serve to decouple URLs from Python

code.

Here’s what a URLconf might look like for the Reporter/Article example above:

Listing 4: mysite/news/urls.py

from django.urls import path

from . import views

urlpatterns = [

path('articles/<int:year>/', views.year_archive),

path('articles/<int:year>/<int:month>/', views.month_archive),

path('articles/<int:year>/<int:month>/<int:pk>/', views.article_detail),

]

The code above maps URL paths to Python callback functions (“views”). The path strings use parameter tags to

“capture” values from the URLs. When a user requests a page, Django runs through each path, 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 paths are compiled into regular expressions at load time.

Once one of the URL patterns matches, Django calls the given view, which is a Python function. Each view gets

passed a request object – which contains request metadata – and the values captured in the pattern.

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

article_detail(request, year=2005, month=5, pk=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:

10 Chapter 2. Getting started

Django Documentation, Release 3.0.2.dev

Listing 5: mysite/news/views.py

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)

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:

Listing 6: mysite/news/templates/news/year_archive.html

{% 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 %}

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.

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:

2.1. Django at a glance 11

Django Documentation, Release 3.0.2.dev

Listing 7: mysite/templates/base.html

{% load static %}

<html>

<head>

<title>{% block title %}{% endblock %}</title>

</head>

<body>

{% block content %}{% endblock %}

</body>

</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 means that a site redesign can be done by 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 by only 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 lets you create RSS and Atom feeds by writing a small Python class.

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

The next 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 minimal installation that’ll work while you walk through the introduction.

2.2.1 Install Python

Being a Python Web framework, Django requires Python. See What Python version can I use with Django? for details.

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

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

ager.

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

12 Chapter 2. Getting started

Django Documentation, Release 3.0.2.dev

• 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 in a shell prompt (indicated by the $ preﬁx):

$ python -m django --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 3.0, which supports Python 3.6 and 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’re using an older version of Python, check What Python version

can I use with Django? to ﬁnd a compatible version of Django.

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

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:

14 Chapter 2. Getting started

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