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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
61. None

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
76. None

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. [email protected]