building pluggable web applications using django

Introduction Using django Features of django Reuseable apps End Notes

Building Pluggable Web Applications using

Lakshman Prasad

Agiliq Solutions

April 21, 2010


• For building database driven web applications

• Emphasis on Reuse, DRY and simplicity


Hypothetical Application


Install a pluggable app django-star-rating

$pip install django-star-rating

INSTALLED APPS = (’ d jango . c o n t r i b . auth ’ ,’ d jango . c o n t r i b . c o n t e n t t y p e s ’ ,’ d jango . c o n t r i b . s e s s i o n s ’ ,’ d jango . c o n t r i b . s i t e s ’ ,’ d jango . c o n t r i b . admin ’ ,’ s t a r r a t i n g ’ ,

)


Point to an url pattern

from b l o g . models import Post

u r l p a t t e r n s = p a t t e r n s ( ’ ’ ,( r ’ ˆ$ ’ , ’ b l o g . v i e w s . i n d e x ’ ) ,( r ’ s t a r i n g /$ ’ ,{model : Post } ,’ s t a r r a t i n g . v i e w s . s t a r ’ ) ,

)


Put the rating where you want!

<html><head>

< t i t l e>{{ page . t i t l e }}</ t i t l e><body>

{% s t a r r a t i n g %}<div>

{{ page . c o n t e n t }}</ div>

. . .</body>

. . .


Thats it!


IntroductionDefinitionA Case Study: Youtube StarsOverviewPhilosophy

Using djangoMTV

Features of djangoFeatures

Reuseable appsWriting reuseable appsCommunity Applications

End NotesDjango StatsCommon Enterprise HurdlesOther


Developed at Lawrence-Journal World

5 million hits per month

600 Contributors

Majority of the features community contributed

5 years since Open Source


Philosophy

Automate repetitive tasks

Make Development Fast


Convention Over Configuration

Follow Best Practices

Models-Templates-Views

Models


Model Syntax

from django . db import models

c l a s s Post ( models . Model ) :t i t l e = models . C h a r F i e l d ( m a x l e n g t h =100)t e x t = models . T e x t F i e l d ( )d a t e t i m e = models . DateTimeFie ld ( )

c l a s s Meta :o r d e r i n g = ( ’−d a t e t i m e ’ , )

def u n i c o d e ( s e l f ) :return s e l f . t i t l e

c l a s s Comment ( models . Model ) :p o s t = models . Fore ignKey ( Post )t e x t = models . T e x t F i e l d ( )


Model API

>>>from b l o g . models import Post , Comment>>>p o s t = Post . o b j e c t s . a l l ( ) [ 0 ]>>>post comments = p o s t . comment set . a l l ( )


Admin by models alone


Admin Syntax

from django . c o n t r i b import adminfrom models import Post , Comment

c l a s s PostAdmin ( admin . ModelAdmin ) :l i s t d i s p l a y = ( ’ t i t l e ’ , ’ d a t e t i m e ’ )

c l a s s CommentAdmin ( admin . ModelAdmin ) :l i s t d i s p l a y = ( ’ t e x t ’ , )

admin . s i t e . r e g i s t e r ( Post , PostAdmin )admin . s i t e . r e g i s t e r ( Comment , CommentAdmin )

List Page

Add an Entry

Auto Validation


Ugly urls

h t t p : / / a r t . com/ a r t g a l l e r y / d e f a u l t . asp ?s i d =9DF4BC0580DF11D3ACB60090271E26A8

&command= f r e e l i s t

h t t p : / / p r e v i e w . ynot . com/ c g i b i n /nd CGI 50 . c g i / YnotPhoenix /CFsMain .


Good urls

h t t p : / /www. w i r e d . com/ a p p l e /MacbookPro/

h t t p : / / devmarch . com/ d e v e l o p e r s u m m i t / s p e a k e r s . html


django url pattern

from b l o g . models import Post

u r l p a t t e r n s = p a t t e r n s ( ’ ’ ,( r ’ ˆ$ ’ , ’ b l o g . v i e w s . i n d e x ’ ) ,( r ’ s t a r i n g /$ ’ ,{model : Post } ,’ s t a r r a t i n g . v i e w s . s t a r ’ ) ,

)


django views

from django . h t t p import HttpResponse

def p o s t ( r e q u e s t ) :return HttpResponse ( ’ H e l l o World ! ’ )


django views

def p o s t ( r e q u e s t , p o s t i d ) :p o s t = Post . o b j e c t s . g e t ( pk=p o s t i d )i f r e q . method == ’POST ’ :

comment form = CommentForm ( r e q u e s t .POST)comment = comment form . s a v e ( )

p a y l o a d = { ’ p o s t ’ : post ,’ comments ’ :Comment . o b j e c t s . f i l t e r ( p o s t i d=p o s t i d ) ,’ comment form ’ : CommentForm ( )}

return r e n d e r t o r e s p o n s e ( ’ p o s t . html ’ ,pay load ,R e q u e s t C o n t e x t ( r e q ) )

Templates


django template

{% e x t e n d s ” base . html ” %}{% b l o c k body %}

{% i f u s e r . i s a u t h e n t i c a t e d %}Welcome {{ u s e r . g e t f u l l n a m e }}

{% e l s e %}{% i n c l u d e ” l o g i n . html ” %}

{% e n d i f %}

. . .

{% e n d b l o c k %}

Features


• Admin Interface

• Generic Views

• Testing Tools

• Sessions

• Authentication

• Caching

• Internationalization

• RSS

• CSRF protection

• File Storage

Django Documentation


General conventions adopted by the community


Use template tags

<p>The t ime i s {% c u r r e n t t i m e ”%I :%M %p” %}.</p>

from django import t e m p l a t edef d o c u r r e n t t i m e ( p a r s e r , token ) :

tag name , f o r m a t s t r i n g = token . s p l i t c o n t e n t s ( )return CurrentTimeNode ( f o r m a t s t r i n g [ 1 : −1 ] )


Use Signals

from django . c o r e . s i g n a l s import r e q u e s t f i n i s h e d

r e q u e s t f i n i s h e d . c o n n e c t ( m y c a l l b a c k )

from django . db . models . s i g n a l s import p r e s a v efrom myapp . models import MyModel

def m y h a n d l e r ( sender , ∗∗ kwargs ) :. . .

p r e s a v e . c o n n e c t ( my handler , s e n d e r=MyModel )


Basics

• Take template_name and extra_context every where

• Write urls in applications

• Import from the application level

• Prefix template name with directory

• Use MEDIA_URL in templates

• Reverse url patterns


Basics Done right

def r e g i s t e r ( r e q u e s t , backend , s u c c e s s u r l=None ,f o r m c l a s s=None ,d i s a l l o w e d u r l=’ r e g i s t r a t i o n d i s a l l o w e d ’ ,template name=’ r e g i s t r a t i o n / r e g i s t r a t i o n f o r m . html ’ ,e x t r a c o n t e x t=None ) :

. . .

return r e n d e r t o r e s p o n s e ( template name ,{ ’ form ’ : form } ,c o n t e x t )


Advanced

• Use Template Response

• Write Views as Classes

There is an app for that

For every size and style


Github Search ”django”


Pinax Features• openid support• email verification• password management• site announcements• a notification framework• user-to-user messaging• friend invitation (both internal and external to the site)• a basic twitter clone• oembed support• gravatar support• interest groups (called tribes)• projects with basic task and issue management• threaded discussions• wikis with multiple markup support• blogging• bookmarks• tagging• contact import (from vCard, Google or Yahoo)• photo management


django-mingus

d j a n g o e x t e n s i o n sb a s i cf l a t b l o c k sd i s q u snavbard j a n g o d b l o gs o r loembdedt e m p l a t e u t i l sd j a n g o p r o x yc o m p r e s s o rd jango markupg o o g l e a n a l y t i c s

v i e w c a c h e u t i l sc o n t a c t f o r mhoneypots u g a rquotemedjango− s t a t i c f i l e sdjango−b i t l ydjango−t w i t t e rpython−t w i t t e rdjango−wysiwygdjango−s l i m m e rdjango−c r o p p e rdjango−r e q u e s t

Django users


Popular Users

• Media• LA Times• NY Times• Washington Post• Guardian

• Web2.0• Mahalo: 10 million Page views• Pownce, SixApart

• Full List: djangosites.com


NASA

After an extensive trade study, we selected Django ...as the first and primary application environment for theNebula Cloud.


Enterprise Adoption Hurdles

• Multiple Databases

• Dynamic settings infrastructure

• Tools


About Me• [email protected], @becomingGuru• lakshmanprasad.com• Agiliq Solutions Formerly, Usware Technologies @agiliq• Team of Expert Django Developers, Happy Clients

http://www.agiliqsolutions.com/


Image Attributions

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