Django 2.1官方指南：入门与核心功能详解

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Django 2.1官方文档是Django软件基金会提供的权威指南，针对这个版本，文档详细地介绍了Django框架的各项核心功能和开发流程，旨在帮助新用户快速上手，同时也为有经验的开发者提供深入理解框架的资料。以下是文档的主要内容概览： 1. 入门与帮助： - 提供获取帮助的途径，包括官方论坛、邮件列表、Stack Overflow等社区资源，便于解决初学者在使用过程中遇到的问题。 - 文档结构清晰，逐步引导读者了解Django的组织架构，如模型层（Model）、视图层（View）和模板层（Template），这些都是构建Web应用的基础。 2. 核心组件： - 模型层：讲解如何定义数据库模型，包括模型类的定义、字段类型、查询操作等，这是数据持久化和业务逻辑的核心部分。 - 视图层：介绍如何处理HTTP请求，创建响应，以及视图函数的编写，涉及URL路由、模板渲染和中间件的使用。 - 表单系统：阐述如何设计和处理用户输入，包括表单的定义、验证、以及与视图的交互。 - 开发过程：涵盖版本控制、测试策略、部署指导等内容，确保项目的稳定和高效开发。 3. 管理工具与安全： - 管理后台（Admin）：演示如何使用内置的管理站点来创建、编辑和删除模型实例，以及自定义模型的管理界面。 - 安全性：讨论了身份验证、授权、CSRF保护等关键安全措施，确保应用的用户数据安全。 4. 国际化与性能优化： - 国际化（i18n）与本地化（l10n）：如何处理多语言支持和时区问题，提高应用的全球化能力。 - 性能与优化：提供了一些实用的技巧和最佳实践，帮助开发者识别并改进应用性能瓶颈。 5. 附加功能： - 地理位置框架：如果应用需要地理位置相关功能，文档会介绍如何集成和使用。 - 其他核心功能：如静态文件管理、中间件、缓存机制等，都是提升应用功能和用户体验的重要组成部分。 6. 开源项目介绍： - 文档还介绍了Django作为开源项目的背景、社区参与方式以及贡献指南，鼓励开发者参与到Django的发展中来。 2.0版的“Getting Started”部分详尽地介绍了如何快速上手Django，从安装、基础设置到编写第一个Django应用的全过程，包括分步教程，让新手能够循序渐进地掌握框架的用法。此外，还有高级教程，深入探讨如何编写可重用的库或插件，以及后续学习路径的推荐。 Django 2.1官方文档是一份全面且实用的指南，无论你是初次接触Django的新手，还是希望深入学习和改进已有项目的开发者，都能从中获得所需的资源和支持。阅读这份文档，将有助于你迅速成为Django开发的高手。

Django Documentation, Release 2.1.5.dev20181224213614

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 just 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 simple 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:

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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 2.1.5.dev20181224213614

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 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. 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:

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• 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 2.1, which supports Python 3.5 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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