Django Architecture Introduction

Python Web Framework
ZaneboChen

Agenda
2
 Introduction
 Model, View, Control(MVC)
 Django Architecture(MTVC)
 Project / Site creation
 Settings
 Project structure
 Features
 Why use it?
 Future
 Questions

Introduction
3
Django is a high-level Python Web framework that encourages rapid
development and clean, pragmatic design.(快速,实用开发.)
The Web framework for perfectionists with deadlines.(期限终结者)
Django makes it easier to build better Web apps more quickly and
with less code.(用少量地代码快速创建)
 Encourages rapid development and clean, pragmatic design.
 Named after famous Guitarist Django Reinhardt
 Developed by Adrian Holovaty & Jacob Kaplan-moss
 Created in 2003, open sourced in 2005
 1.0 Version released in Sep 3 2008, now 1.7.1

Introduction
Web Development Concept:
1.用户向Web服务器请求一个文档.
2.Web服务器随即获取或者生成这个文档.
3.服务器再把这个结果返回给浏览器.
4.浏览器将这个文档渲染出来.
三个概念:
通信: HTTP, URL, 请求, 响应.
数据存储: SQL, NOSQL.
表示: 将模板渲染成HTML或其他格式.
4
基本难题: 1.如何将一个请求路由到能够处理它的代码逻辑处?
2.如何动态地将数据显示在HTML文件?

5
Model, View, Control(MVC)
Model(模型层):
控制数据,与DB交互.
View(表示层):
定义显示的方法,用户可见.
Control(控制层):
在模型层与表示层之间斡旋,并且让用
户以请求和操作数据.

6
Django Architecture(MTVC)
Models Describes your data
Views Controls what users sees
Templates How user sees it
Controller URL dispatcher
1.URL调度中心(urls.py)通过匹配相应的URL,将请求移交并调用
相应的视图函数.若相应版本的缓存页存在则直接返回.django
不仅提供页面级别的缓存功能,也提供更加细粒度的缓存.
2.视图函数(views.py)一般会通过读写数据库,或者其他任务,响
应请求.
3.模型(models.py)定义了python中的数据结构及相关数据库交
互操作.除了关系型数据库(Mysql, PostgreSQL,SQLite等)之外,
其他的存储机制如XML,文本文件,LDAP等非关系型数据库也是支
持的.
4.执行完相应的操作后,视图函数一般会返回HTTP响应对象(数据
一般通过模板输出)给浏览器.在返回之前,视图函数也可以选择
把响应对象存储在缓存中.
5.模板系统返回HTML页面.Django模板提供易于上手的语法,足以
实现表示逻辑的所有需求.

7
Django Architecture(MTVC)
M
Model
V
View
C
Controll
er
M
Model
T
Templ
ate
V
View
C
Contro
ller
Django
Framework

9
Django Middleware
During the request phase :
process_request(request)
process_view(request, view_func,
view_args, view_kargs)
During the response phase:
process_exception(request, exception)
(only if the view raised an exception)
process_template_response(request,
response)
(only for template responses)
process_response(request, response)

10
Installation
Prerequisites
 Python
 PIP for installing Python packages (http://www.pip-installer.org/en/latest/installing.html)
 pip install Django==1.6.5
o OR https://www.djangoproject.com/download/ - python setup.py install
 pip install mysql-python
o MySQL on windows https://pypi.python.org/pypi/MySQL-python/1.2.4
 Add Python and Django to env path
o PYTHONPATH D:Python27
o Path D:Python27; D:Python27Libsite-packages; D:Python27Libsite-packagesdjangobin;
 Testing installation
o shell> import django; django.VERSION;

11
Project / Site Creation
 Creating new Project
 django-admin.py startproject demoproject
A project is a collection of applications
 Creating new Application
 python manage.py startapp demosite
An application tries to provide a single, relatively self-contained set of related functions
 Using the built-in web server
 python manage.py runserver
 python manage.py runserver 80
Runs by default at port 8000
It checks for any error and validate the models. Throws errors/warnings for any misconfigurations and invalid
entries.

12
# urls.py
from django.conf.urls import patterns, url
import views
urlpatterns = patterns('',
url(r'^$', views.index),
url(r'^test/P<id>(d+)/$', views.test),
)
# views.py
from django.shortcuts import render
from models import TestModel
def index(request):
return render(request, 'index.html', {‘text’: ‘hello world!’ })
def test(request, id):
model = TestModel.objects.get_or_create(id=id)
return render(
request, 'test.html', {'model ': model}
)

13
# models.py
from django.db import models
import datetime
Class TestModel(models.Mode):
# admin.py
from django.contrib import admin
from models import TestModel
admin.site.register(TestModel)
username = models.CharField(max_length=20)
create_time = models.DateTimeField(default=datetime.datetime.now)

15
Settings
 Project settings.py overrides from <python>/Lib/site-packgaes/django/conf/global_settings.py
 Set DJANGO_SETTINGS_MODULE for your Project, tells django which settings to be used. (demoproject.settings)
 export/set DJANGO_SETTINGS_MODULE=demoproject.settings
 For server mod_wsgi: os.environ['DJANGO_SETTINGS_MODULE'] = 'demoproject.settings'
 DEBUG True or False
 DATABASES: {ENGINE, NAME) 'mysql', 'sqlite3' , 'oracle‘ or ‘mongodb’.. etc
 ROOT_URLCONF
 INSTALLED_APPS To any app you want to add into your project. Name, Lable must be unique.
 MIDDLEWARE_CLASSES A tuple of middleware classes which process request, response, exceptions to use.
 STATIC_ROOT To any server static files. (can add more dirs to STATICFILES_DIRS) STATICFILES_FINDERS.
 STATIC_URL To serve static files.
 TEMPLATE_DIRS Template directories
Using settings in Python code
from django.conf import settings
if settings.DEBUG:
# Do something

16
Project Directory Structure
demosite/ ---------------------------------- Just a container for your project. Its name doesn’t matter to Django;
manage.py ------------------------- A command-line utility that lets you interact with this Django project in various ways.
demosite/ ------------------------- Actual Python package for your project. Use this name to import anything inside it
__init__.py ----------------- A file required for Python to treat the demosite directory as a package.
settings.py ----------------- Settings/configuration for this Django project
urls.py ---------------------- Root URL config, the URLs for this Django project, provides mapping to views
wsgi.py ---------------------- An entry-point for WSGI-compatible webservers to serve your project
demoapp/ -----------------
__init__.py --------
migrations/ -----as a version control of database schema. Packaging up your model change into individual migration files.
urls.py ------------ URL Configuration of your app, include in Root URL.
views.py ---------- Responsible for processing a user’s request and for returning the response
conf.py --------- Separate Settings of your own app. Can override by project settings. By using django-appconf.
models.py --------- A model is the single, definitive source of information about your data.
admin.py ---------- It reads metadata in your model to provide a powerful and production-ready interface
forms.py ----------- To create and manipulate form data
static/demoapp/ --- Static file of your app. python manage.py collectstatic in production, copy all to STATIC_ROOT.
templates/demoapp/ ----------- Templates file of your app. In project, loader.get_template(‘demoapp/index.html’)
templates/ ----------------- HTML files , renders based on views. You can change to any dir, configurable in settings.py
static/ ----------------------- CSS, JS, images.. etc, configurable in settings.py

17
Features
 Object Relational Mapper – ORM
 MVC (MVTC) Architecture
 Focuses on automating as much as possible and adhering to the DRY principle
 Template System
 Out of the box customizable Admin Interface, makes CRUD easy
 Built-in light weight Web Server
 Elegant URL design
 Reverse resolution of URLS.
 Custom Middleware
 Authentication / Authorization
 Internationalization, Time Zone support
 Cache framework, with multiple cache mechanisms
 Free, and Great Documentation

18
Why use django?
 Everything is Python Package
 Django, Third Party Packages, Your Application, Your Site
 monkey patch.(simply the dynamic replacement of attributes at runtime.)
 Virtualenv虚拟环境搭建.
 Pip 强大的库管理.setup.py,自由发布.
 Batteries.(自带电池,各种第三方库.)
 db, forms, templates, views, middleware, test
 migrations, auth, admin, cache, sessions, gis.
Bench: jinjia2, SQLALchemy, Rhetoric, django-xadmin, South.
 文档齐全,活跃的社区.
 https://www.djangopackages.com/
 https://www.djangoproject.com/
 http://www.django-rest-framework.org/
 https://djangosnippets.org/

20
Django admin for mongo
django.forms(处理用户交互):
1. 准备并处理需要被展示的数据.
2. 为数据创建HTML的展示形式.(表单,<form>,css,js)
3. 接收,处理并校验来自客户端的提交数据.
django.forms.widgets:
1. HTML元素在django中的表示, render直接返回html元素.
2. 从相应的html元素中获取用户输入.
区别与联系:
Forms是对输入的验证逻辑,并且直接用于template中.
Widgets负责渲染html元素和抽取用户原始输入.
两者一般是结合使用,widgets需要在forms中被指定.

22
Django admin for mongo
权限管理:
添加,修改,浏览,删除. 四种权限.支持分组管理
1.利用Django自带的admin后台权
限管理系统.
2.每个Mongo Collection对应关系
型数据库中的一个空表.(仅有表名)
3.对sql表进行权限管理.

24
Questions
Q:
Have you considered using Django and found good reasons not to do so?
A:
Yeah, I am an honest guy, and the client wanted to charge by the hour.
There was no way Django was going to allow me to make enough money.

Django Architecture Introduction

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