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1. Introduction Paradigms The Admin Interface The Django Advantage Djangoic approach to implement common web development paradigms Lakshman Prasad April 20, 2011
2. Concepts and abstractions used to represent elements of a program
3. CS is neither about computers nor is science - Abelson, SICP, MIT
4. Web Development Paradigms: Modeling common web patterns
5. Introduction Paradigms The Admin Interface The Django Advantage Why
6. Introduction Paradigms The Admin Interface The Django Advantage • For building database driven web applications
7. Introduction Paradigms The Admin Interface The Django Advantage • For building database driven web applications • Emphasis on Reuse, DRY and simplicity
8. Batteries Included
9. docs.djangoproject.com
10. Lets examine the batteries
11. Introduction Paradigms The Admin Interface The Django Advantage About Me • Active Djangonaut and active in Python world • Part of a few popular open source django applications github.com/becomingGuru. • Co-Authored an ebook ”django-design-patterns” • Architect and develop django applications at InMobi • Earlier, Consulting and Development via Agiliq Solutions • Developed several custom proprietory django applications • twitter.com/becomingGuru http://becomingguru.com
12. Introduction Paradigms The Admin Interface The Django Advantage A nerd, for a while
13. consulting since, until recently
14. Always been developing
15. Work at InMobi now
16. Introduction Paradigms The Admin Interface The Django Advantage Introduction Definition About Me Abstractions Paradigms Forms Authentication/Caching/Sessions Inernational/Human/Local ..ization Generic Views Sorting/Pagination/DataBrowse/GRID/Messages/Other The Admin Interface Admin Databrowse The Django Advantage Users Community Endnotes
17. Software span a spectrum
18. Those that interact with hardware
19. The nuts and bolts
20. Those that solve a human problem ...
21. ... that are Complex Systems
22. Frameworks come in between ...
23. ... to achieve balance ...
24. ... and reduce cost of maintainance and development
25. Include all desktop and web frameworks
26. Forms
27. Save form data to a table
28. Introduction Paradigms The Admin Interface The Django Advantage Use a Model Form >>> from django . forms import ModelForm # Create the form c l a s s . >>> class ArticleForm ( ModelForm ) : . . . class Meta : . . . model = A r t i c l e # Creating a form to add an a r t i c l e . >>> form = ArticleForm () # Creating a form to change an e x i s t i n g a r t i c l e . >>> a r t i c l e = A r t i c l e . o b j e c t s . get ( pk=1) >>> form = ArticleForm ( i n s t a n c e=a r t i c l e )
29. Introduction Paradigms The Admin Interface The Django Advantage Save Foreign Keys
30. Introduction Paradigms The Admin Interface The Django Advantage Use Model Formset from django . forms . models import m o d e l f o r m s e t f a c t o r y AuthorFormSet = m o d e l f o r m s e t f a c t o r y ( Author ) formset = AuthorFormSet () > > > p r i n t formset <i n pu t type=” hidden ” name=”form− TOTAL FORMS” v a l u e=”1” i d=” id form− TOTAL FORMS” /> <i n pu t type=” hidden ” name=”form−INITIAL FORMS” v a l u e=”0” i d=” id form−INITIAL FORMS” /> <i n pu t type=” hidden ” name=”form− MAX NUM FORMS” i d=” id form− MAX NUM FORMS” /> <tr> <th> <l a b e l f o r=” id form −0 −name”>Name:</ l a b e l > </th> <td> <i n pu t i d=” id form −0 −name” type=” t e x t ” name=”form−0 −name” maxlength=”100” /> </td> </tr>
31. Introduction Paradigms The Admin Interface The Django Advantage Model Formset options formset = AuthorFormSet ( qs=Author . o b j e c t s . a l l () , e x t r a =5) formset . i s v a l i d () formset . e r r o r s { ’name ’ : ’ This f i e l d i s r e q u i r e d ’ } formset . changed forms formset . save ()
32. Introduction Paradigms The Admin Interface The Django Advantage Form pre populated
33. Introduction Paradigms The Admin Interface The Django Advantage Forms dont have to save to a Model from django import forms class ContactForm ( forms . Form ) : s u b j e c t = forms . CharField ( max length =100) message = forms . CharField () sender = forms . E mail Fie ld () c c m y s e l f = forms . BooleanField ( r e q u i r e d=False ) def save ( s e l f ) : #Do anything . . .
34. Form Preview
35. Introduction Paradigms The Admin Interface The Django Advantage Form Preview from django . c o n t r i b . formtools . preview import FormPreview from myapp . models import SomeModel #Add a u r l ( r ’ ˆ post /$ ’ , SomeModelFormPreview ( SomeModelForm )) , #Define form preview class SomeModelFormPreview ( FormPreview ) : def done ( s e l f , request , cleaned data ) : # Do something with the cleaned data , then # r e d i r e c t to a ” s u c c e s s ” page . return HttpResponseRedirect ( ’ /form/ s u c c e s s ’ )
36. Form Wizard
37. Introduction Paradigms The Admin Interface The Django Advantage Form Wizard class ContactWizard ( FormWizard ) : def done ( s e l f , request , f o r m l i s t ) : do something with the form data ( f o r m l i s t ) return HttpResponseRedirect ( ’ / r e d i r e c t / ’ )
38. Introduction Paradigms The Admin Interface The Django Advantage CSRF Protection <form a c t i o n=”” method=” post ”>{% c s r f t o k e n %} from django . views . d e c o r a t o r s . c s r f import c s r f p r o t e c t from django . template import RequestContext @ c s r f p r o t e c t def my view ( request ) : c = {} # . . . return r e n d e r t o r e s p o n s e ( ” a template . html” , c , c o n t e x t i n s t a n c e= RequestContext ( request ))
39. Introduction Paradigms The Admin Interface The Django Advantage Authentication: Point to url pattern u r l p a t t e r n s += p a t t e r n s ( ’ django . c o n t r i b . auth . views ’ , u r l ( r ’ ˆ l o g i n /$ ’ , ’ l o g i n ’ ) , u r l ( r ’ ˆ logout /$ ’ , ’ logout ’ ) , u r l ( r ’ ˆ r e g i s t e r /$ ’ , ’ r e g i s t e r ’ ) , u r l ( r ’ ˆ p a s s r e s e t /$ ’ , ’ p a s s w o r d r e s e t ’ ) , u r l ( r ’ ˆ p a s s r e s e t 2 /$ ’ , ’ password reset done ’ ) , u r l ( r ’ ˆ p a s s r e s e t c o n f i r m /(?P<uidb36 >[−\w]+)/ ’ , ’ p a s s w o r d r e s e t c o n f i r m ’ ) , u r l ( r ’ ˆ p as s r e s e t c o m p l e t e /$ ’ , ’ password reset complete ’ ) , )
40. Introduction Paradigms The Admin Interface The Django Advantage Login Required from django . c o n t r i b . auth . d e c o r a t o r s import \ l o g i n r e q u i r e d @ l o g i n r e q u i r e d ( r e d i r e c t f i e l d n a m e=’ r e d i r e c t t o ’ ) def my view ( request ) : . . .
41. Introduction Paradigms The Admin Interface The Django Advantage Authentication backends class SettingsBackend : ””” Authenticate a g a i n s t the s e t t i n g s ADMIN LOGIN and ADMIN PASSWORD. ””” def a u t h e n t i c a t e ( s e l f , username=None , password=None ) i f l o g i n v a l i d and pwd valid : return user return None def g e t u s e r ( s e l f , u s e r i d ) : try : return User . o b j e c t s . get ( pk=u s e r i d ) except User . DoesNotExist : return None
42. django-socialauth
43. Introduction Paradigms The Admin Interface The Django Advantage Open ID backend c l a s s OpenIdBackend : def a u t h e n t i c a t e ( s e l f , openid key , request , p r o v i d e r , u s e r=None ) : t r y : assoc = U s e r A s s o c i a t i o n . o b j e c t s . get ( openid key=openid key ) return assoc . u s e r except U s e r A s s o c i a t i o n . DoesNotExist : #f e t c h i f openid p r o v i d e r p r o v i d e s any simple r e g i s t r a t i o n f i e l d s i f r e q u e s t . openid and r e q u e s t . openid . s r e g : email = r e q u e s t . openid . s r e g . get ( ’ email ’ ) nickname = r e q u e s t . openid . s r e g . get ( ’ nickname ’ ) firstname , lastname = ( r e q u e s t . openid . s r e g . get ( ’ fullname ’ , ’ ’ ) return u s e r def GooglesAX ( s e l f , o p e n i d r e s p o n s e ) : email = ( o p e n i d r e s p o n s e . ax . g e t S i n g l e ( ’ http :// axschema . org / contact / email ’ )) f i r s t n a m e = ( o p e n i d r e s p o n s e . ax . g e t S i n g l e ( ’ http :// axschema . org /namePerson/ f i r s t ’ )) lastname = ( o p e n i d r e s p o n s e . ax . g e t S i n g l e ( ’ http :// axschema . org /namePerson/ l a s t ’ )) return l o c a l s () def g e t u s e r ( s e l f , u s e r i d ) : t r y : u s e r = User . o b j e c t s . get ( pk=u s e r i d ) return u s e r except User . DoesNotExist : return None
44. ”Normalized data is for sissies” - Cal Henderson
45. Introduction Paradigms The Admin Interface The Django Advantage Different blocks need different caching durations
46. Introduction Paradigms The Admin Interface The Django Advantage Generally Memcache Every page CACHE BACKEND = ’ memcached : / / 1 2 7 . 0 . 0 . 1 : 1 1 2 1 1 / ’ CACHE BACKEND = ’ memcached : //1 72. 19. 26. 240 :11 211 ;\ 172.19.26.242:11212;172.19.26.244:11213/ ’
47. Introduction Paradigms The Admin Interface The Django Advantage Implement a caching decorator from django . core . cache import cache def c a c h e f o r ( seconds , f e t c h =0): def c a c h e i t ( func ) : def deco func ( s e l f ) : v a l = cache . get ( s e l f . get cache key ( f e t c h )) i f not v a l : v a l = func ( s e l f ) cache . s e t ( s e l f . get cache key ( f e t c h ) , val , seconds ) return v a l return deco func return c a c h e i t
48. Introduction Paradigms The Admin Interface The Django Advantage Apply on the blocks class TwitterBlock ( TwitterSearchBlock ) : template name = ’ t w i t t e r u s e r b l o c k . html ’ a j a x t em p l at e = ’ t w e e t s u s e r . html ’ @cache for (60∗60 , f e t c h =1) def f e t c h d a t a ( s e l f ) : tw = Twitter ( email=’ umoja com ’ ) u s e r t w e e t s = tw . s t a t u s e s . u s e r t i m e l i n e ( screen name=s e l f . data ) return user tweets , None
49. Introduction Paradigms The Admin Interface The Django Advantage Different cache Backends • Database • File System • Local Memory • Redis, a NoSQL store • Dummy- For Development • Sessions can use any of these, or the database.
50. Introduction Paradigms The Admin Interface The Django Advantage Humanization and Localization 19 Apr 2010| naturalday becomes ‘ yesterday ‘ . 20 Apr 2010| naturalday becomes ‘ today ‘ . 1| o r d i n a l becomes ‘1 st ‘ . 2| o r d i n a l becomes ‘2nd ‘ . 1000000| intword becomes ‘1.0 m i l l i o n ‘ . 1200000| intword becomes ‘1.2 m i l l i o n ‘ . {{ value | l o c a l i z e }}
51. Introduction Paradigms The Admin Interface The Django Advantage Internationalization {% b l o c k t r a n s with amount=a r t i c l e . p r i c e %} That w i l l cost $ {{ amount }}. {% endblocktrans %} {% b l o c k t r a n s with myvar=value | f i l t e r %} This w i l l have {{ myvar }} i n s i d e . {% endblocktrans %} class in . forms . I N S t a t e F i e l d class in . forms . INZipCodeField class in . forms . I N S t a t e S e l e c t
52. Introduction Paradigms The Admin Interface The Django Advantage Using Generic Views # some app/ views . py from django . views . g e n e r i c import TemplateView class AboutView ( TemplateView ) : template name = ” about . html” # u r l s . py from django . conf . u r l s . d e f a u l t s import ∗ from some app . views import AboutView u r l p a t t e r n s = p a t t e r n s ( ’ ’ , ( r ’ ˆ about / ’ , AboutView . as view ( ) ) , )
53. Introduction Paradigms The Admin Interface The Django Advantage List and Object Views from django . views . g e n e r i c import ListView from books . models import Book class AcmeBookListView ( ListView ) : context object name = ” b o o k l i s t ” queryset = Book . o b j e c t s . f i l t e r ( publisher name= ”Acme P u b l i s h i n g ” ) template name = ” books / a c m e l i s t . html”
54. Introduction Paradigms The Admin Interface The Django Advantage Mixins from django import http from django . u t i l s import s i m p l e j s o n as j s o n c l a s s JSONResponseMixin ( o b j e c t ) : def r e n d e r t o r e s p o n s e ( s e l f , context ) : ” Returns a JSON r e sponse c o n t a i n i n g ’ context ’ as payload ” return s e l f . g e t j s o n r e s p o n s e ( s e l f . c o n v e r t c o n t e x t t o j s o n ( context )) def g e t j s o n r e s p o n s e ( s e l f , content , ∗∗ h t t p r e s p o n s e k w a r g s ) : ” Construct an ‘ HttpResponse ‘ o b j e c t . ” return http . HttpResponse ( content , c o n t e n t t y p e=’ a p p l i c a t i o n / j s o n ’ , ∗∗ h t t p r e s p o n s e k w a r g s ) def c o n v e r t c o n t e x t t o j s o n ( s e l f , context ) : ” Convert the context d i c t i o n a r y i n t o a JSON o b j e c t ” return j s o n . dumps ( context )
55. Introduction Paradigms The Admin Interface The Django Advantage Any combinations of Mixins c l a s s HybridDetailView ( JSONResponseMixin , SingleObjectTemplateResponseMixin , BaseDetailView ) : def r e n d e r t o r e s p o n s e ( s e l f , context ) : # Look f o r a ’ format=j s o n ’ GET argument i f s e l f . r e q u e s t .GET. get ( ’ format ’ , ’ html ’ ) == ’ j s o n ’ : return JSONResponseMixin . r e n d e r t o r e s p o n s e ( s e l f , context ) e l s e : return SingleObjectTemplateResponseMixin . r e n d e r t o r e s p o n s e ( s e l f , context )
56. Introduction Paradigms The Admin Interface The Django Advantage Types of Generic Views • Simple: Redirect, Render to Template • Detail, List View • Archive View: Date, Month, Year views • Basic CRUD, with or w/o Auth
57. Introduction Paradigms The Admin Interface The Django Advantage Builtin support for Pagination >>> from django . core . paginator import Paginator >>> o b j e c t s = [ ’ john ’ , ’ paul ’ , ’ george ’ , ’ r i n g o ’ ] >>> p = Paginator ( objects , 2) >>> p . count 4 >>> p . num pages 2 >>> p . page range [1 , 2] >>> page1 = p . page (1) >>> page1 <Page 1 of 2> >>> page1 . o b j e c t l i s t [ ’ john ’ , ’ paul ’ ]
58. Introduction Paradigms The Admin Interface The Django Advantage Abstract the pagination in middleware django pagenation {% autopaginate o b j e c t l i s t 10 %} {% paginate %}
59. DataGrid enables user customisable column and sorting
60. Introduction Paradigms The Admin Interface The Django Advantage Other common paradigms • Display Image Thumbnail • Store data on a CDN, like Amazon S3 • Periodic tasks with Celery • Decoupled design using Signals • GeoDjango : Framework for all location based applications
62. Introduction Paradigms The Admin Interface The Django Advantage Admin by models alone
63. Introduction Paradigms The Admin Interface The Django Advantage Admin Syntax from django . c o n t r i b import admin from models import Post , Comment class PostAdmin ( admin . ModelAdmin ) : l i s t d i s p l a y = ( ’ t i t l e ’ , ’ datetime ’ ) class 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)
64. List Page
65. Add an Entry
66. Auto Validation
67. Introduction Paradigms The Admin Interface The Django Advantage Databrowse enables browsable web complete with hyperlinks
68. Introduction Paradigms The Admin Interface The Django Advantage Popular Users • Media • LA Times • NY Times • Washington Post • Guardian • Hindustan TImes
69. Introduction Paradigms The Admin Interface The Django Advantage Popular Users • Media • LA Times • NY Times • Washington Post • Guardian • Hindustan TImes • Web2.0 • Mahalo: 10 million Page views • Many web startups: Convore, Lanyard, Everyblock, GroupQuality,
70. Django users
71. Introduction Paradigms The Admin Interface The Django Advantage NASA uses Django After an extensive trade study, we selected Django ... as the first and primary application environment for the Nebula Cloud.
72. 700 contibutors
73. More open source projects than you think ...
74. ... one for every size and style
75. Don’t go where the puck is; go where the puck is going to be
77. Introduction Paradigms The Admin Interface The Django Advantage Image Attributions http ://www. f l i c k r . com/ photos / t e j e d o r o d e l u z /3157690060/ http ://www. f l i c k r . com/ photos /23820645@N05/4287681570/ http ://www. f l i c k r . com/ photos / a i d a n j o n e s /3575000735/ http :// j a c o b i a n . org / http :// s a n j u a n c o l l e g e . edu/ l i b / images / p h i l o s o p h y b r a i n . jpg http ://www. f l i c k r . com/ photos /uhop /105062059/ http :// s3 . amazonaws . com/memebox/ uploads /136/ e x p o n e n t i a l g r a p h 2 . jpg http :// geekandpoke . typepad . com/ geekandpoke / images /2008/06/03/ s e x p l 1 8 . jpg http ://www. f l i c k r . com/ photos /go /253819/ http :// aroundthesphere . f i l e s . wordpress . com/2009/05/ swiss−army−k n i f e . jpg http ://www. f r e e f o t o . com/ images /41/04/41 04 9− − −Keep−Left web . jpg http ://www. f l i c k r . com/ photos / o r i n r o b e r t j o h n /114430223/
78. hello@lakshmanprasad.com