Django框架入门与核心功能详解

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Django教程是一份详细的指南，它涵盖了Python语言的Web框架——Django的各个方面。该教程适用于初学者和经验丰富的开发者，帮助他们理解并掌握Django的核心组件和开发流程。首先，文档介绍部分分为几个主要部分： 1.1 获取帮助：文档提供多种途径获取支持，包括官方文档、社区论坛、邮件列表以及Stack Overflow等平台。 1.2 文档组织：文档按照层次结构编排，清晰地介绍了从入门到深入的概念，便于学习者逐步探索。 1.3 首步：这部分介绍了如何安装和设置Django环境，以及创建第一个项目的基本步骤。 1.4 模型层：模型层是Django的核心概念，涵盖了数据库设计、模型定义和管理对象的处理。 1.5 视图层：这部分讲解了如何创建和组织视图函数，以及与模型层交互来响应用户的请求。 1.6 模板层：模板系统是Django用来呈现动态内容的关键，包括模板语法、模板继承和过滤器的使用。 1.7 表单：Django的表单处理功能强大，涵盖了表单定义、验证和数据绑定的详细介绍。 1.8 开发过程：涉及版本控制、测试用例编写、部署策略等内容，确保高效、稳定的开发实践。 1.9 管理后台（Admin）：Django内置的管理界面，用于快速管理数据库模型和数据。 1.10 安全性：涵盖身份验证、授权和会话管理，确保应用程序的安全性。 1.11 国际化与本地化：如何让应用适应不同语言和地区，实现多语言支持。 1.12 性能与优化：关注代码性能调优、缓存机制和资源管理等方面。 1.13 Python兼容性：解释Django与不同Python版本的兼容性，以及对新版本的更新和支持。 1.14 地理框架：如果需要在地理位置上进行应用开发，这部分提供了相关支持。 1.15 其他核心功能：涵盖了如静态文件管理、中间件、信号系统等其他关键功能的介绍。 1.16 Django开源项目：讲述了Django作为一个开源项目的背景、社区贡献以及参与贡献的方式。 2.0 部分则是具体的实战教程，包括从安装到编写第一个Django应用的详细步骤，以及高级主题——如何创建可重用的应用。 Django教程是一个全面的资源，不仅适合初学者快速上手，还为进阶开发者提供了深入理解和实践的机会。通过学习这份文档，开发者可以掌握Django的方方面面，构建出功能强大的Web应用。

Django Documentation, Release 1.11.3.dev20170628014239

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.

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:

mysite/news/urls.py

from django.conf.urls import url

from . import views

urlpatterns = [

url(r'^articles/([0-9]{4})/$', views.year_archive),

url(r'^articles/([0-9]{4})/([0-9]{2})/$', views.month_archive),

url(r'^articles/([0-9]{4})/([0-9]{2})/([0-9]+)/$', views.article_detail),

]

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').

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:

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)

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

for non-programmers to use.

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:

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:

mysite/templates/base.html

{% load static %}

<html>

<head>

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

</head>

<body>

{% block content %}{% endblock %}

</body>

</html>

2.1. Django at a glance 11

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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.

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!

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.

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.

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 3.4.x

[GCC 4.x] on linux

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

>>>

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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 1.11 and Python 3.4 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.

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:

mysite/

manage.py

mysite/

14 Chapter 2. Getting started

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