1. Introduction Forms Authentication Generic Views Caching Others Admin
Web Development Paradigms and djangoic
approach to deal with them.
Lakshman Prasad
Agiliq Solutions
September 25, 2010

2. Concepts and abstractions used to represent elements of a program

3. Web Development Paradigms: Modeling common web patterns

4. Why?

6. Batteries Included

7. docs.djangoproject.com

8. Webapp: Simple web application framework (with custom APIs)

9. Lets examine the batteries

10. Introduction Forms Authentication Generic Views Caching Others Admin
How do I know about web development or django
• Active Djangonaut
• Part of a few popular open source django applications
github.com/becomingGuru, github.com/agiliq
• Consulting and Development via
• Developed several custom proprietory django applications
• @becomingGuru

11. Introduction Forms Authentication Generic Views Caching Others Admin
Introduction
Forms
Authentication
Generic Views
Caching
Others
Admin

12. Forms

13. Save form data to a table

14. Introduction Forms Authentication Generic Views Caching Others Admin
Use a Model Form
>>> from d j a n g o . f o r m s import ModelForm
# C r e a t e t h e form c l a s s .
>>> c l a s s A r t i c l e F o r m ( ModelForm ) :
... c l a s s Meta :
... model = A r t i c l e
# C r e a t i n g a form t o add an a r t i c l e .
>>> form = A r t i c l e F o r m ( )
# C r e a t i n g a form t o c h an ge 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 . g e t ( pk=1)
>>> form = A r t i c l e F o r m ( i n s t a n c e= a r t i c l e )

15. Models

16. Introduction Forms Authentication Generic Views Caching Others Admin
Model Syntax
from d j a n g o . db import m o d e l s
c l a s s P o s t ( m o d e l s . Model ) :
t i t l e = m o d e l s . 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 ( )
datetime = models . DateTimeField ( )
c l a s s Meta :
o r d e r i n g = ( ’−d a t e t i m e ’ , )
def unicode ( self ):
return s e l f . t i t l e
c l a s s Comment ( m o d e l s . Model ) :
post = models . ForeignKey ( Post )
t e x t = models . T e x t F i e l d ( )

17. Introduction Forms Authentication Generic Views Caching Others Admin
Model API
>>>from b l o g . m o d e l s import Post , Comment
>>>p o s t = P o s t . o b j e c t s . a l l ( ) [ 0 ]
>>>p o s t c o m m e n t s = p o s t . c om m en t s et . a l l ( )

18. Introduction Forms Authentication Generic Views Caching Others Admin
Save Foreign Keys

19. Introduction Forms Authentication Generic Views Caching Others Admin
Use Model Formset
from d j a n g o . f o r m s . m o d e l s 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 ( Au t ho r )
f o r m s e t = AuthorFormSet ( )
>>> p r i n t f o r m s e t
<i n p u t t y p e=” h i d d e n ” name=” form−TOTAL FORMS”
v a l u e=” 1 ” i d=” i d f o r m −TOTAL FORMS” />
<i n p u t t y p e=” h i d d e n ” name=” form−INITIAL FORMS”
v a l u e=” 0 ” i d=” i d f o r m −INITIAL FORMS” />
<i n p u t t y p e=” h i d d e n ” name=” form−MAX NUM FORMS”
i d=” i d f o r m −MAX NUM FORMS” />
<t r ><th>
< l a b e l f o r=” i d f o r m −0−name”>Name:</ l a b e l >
</th><td>
<i n p u t i d=” i d f o r m −0−name” t y p e=” t e x t ”
name=” form −0−name” m a x l e n g t h=” 100 ” />
</td ></t r >

20. Introduction Forms Authentication Generic Views Caching Others Admin
Model Formset options
f o r m s e t = AuthorFormSet ( q s=Au th o r . 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 ’ : ’ T h i s f i e l d is required ’}
formset . changed forms
formset . save ()

21. Introduction Forms Authentication Generic Views Caching Others Admin
Form pre populated

22. Introduction Forms Authentication Generic Views Caching Others Admin
Forms dont have to save to a Model
from d j a n g o import f o r m s
c l a s s ContactForm ( f o r m s . Form ) :
s u b j e c t = f o r m s . C h a r F i e l d ( m a x l e n g t h =100)
message = f o r m s . C h a r F i e l d ( )
sender = forms . E m a i l F i e l d ()
c c m y s e l f = f o r m s . B o o l e a n F i e l d ( r e q u i r e d=F a l s e )
def s a v e ( s e l f ) :
#Do a n y t h i n g
...

23. Form Preview

24. Introduction Forms Authentication Generic Views Caching Others Admin
Form Preview
from d j a n g o . c o n t r i b . f o r m t o o l s . p r e v i e w import FormPreview
from myapp . m o d e l s import SomeModel
#Add a u r l
( r ’ ˆ p o s t / $ ’ , SomeModelFormPreview ( SomeModelForm ) ) ,
#D e f i n e form p r e v i e w
c l a s s SomeModelFormPreview ( FormPreview ) :
def done ( s e l f , r e q u e s t , c l e a n e d d a t a ) :
# Do s o m e t h i n g w i t h t h e c l e a n e d d a t a , t h e n
# r e d i r e c t t o a ” s u c c e s s ” page .
r e t u r n H t t p R e s p o n s e R e d i r e c t ( ’ / form / s u c c e s s ’ )

25. Form Wizard

26. Introduction Forms Authentication Generic Views Caching Others Admin
Form Wizard
c l a s s C o n t a c t W i z a r d ( FormWizard ) :
def done ( s e l f , r e q u e s t , f o r m l i s t ) :
do something with the form data ( fo r m l is t )
return HttpResponseRedirect ( ’ / r e d i r e c t / ’ )

27. Authentication

28. Introduction Forms Authentication Generic Views Caching Others Admin
Point to url pattern
u r l p a t t e r n s += p a t t e r n s ( ’ d j a n g o . c o n t r i b . a u t h . v i e w s ’ ,
u r l ( r ’ ˆ l o g i n /$ ’ , ’ l o g i n ’ ) ,
u r l ( r ’ ˆ l o g o u t /$ ’ , ’ l o g o u t ’ ) ,
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 /$ ’ , ’ p a s s w o r d r e s e t d o n e ’ ) ,
u r l ( r ’ ˆ p a s s r e s e t c o n f i r m / ( ?P<u i d b 3 6 >[−w]+)/ ’ ,
’ password reset confirm ’ ) ,
u r l ( r ’ ˆ p a s s r e s e t c o m p l e t e /$ ’ ,
’ password reset complete ’ ) ,
)

29. Introduction Forms Authentication Generic Views Caching Others Admin
Login Required
from d j a n g o . c o n t r i b . a u t h . d e c o r a t o r s import
login required
@ 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 ( r e q u e s t ) :
...

30. Introduction Forms Authentication Generic Views Caching Others Admin
Authentication backends
class SettingsBackend :
”””
A u t h e n t i c a t e a g a i n s t t h e 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 , p a s s w o r d=None )
i f l o g i n v a l i d and p w d v a l i d :
return user
r e t u r n None
def g e t u s e r ( s e l f , u s e r i d ) :
try :
r e t u r n U s e r . o b j e c t s . g e t ( pk=u s e r i d )
except U s e r . D o e s N o t E x i s t :
r e t u r n None

31. django-socialauth

32. Send to template

33. Introduction Forms Authentication Generic Views Caching Others Admin
Generic Views
from d j a n g o . c o n f . u r l s . d e f a u l t s import ∗
from d j a n g o . v i e w s . g e n e r i c . s i m p l e
import d i r e c t t o t e m p l a t e
urlpatterns = patterns ( ’ ’ ,
( ’ ˆ about /$ ’ , d i r e c t t o t e m p l a t e , {
’ t e m p l a t e ’ : ’ a b o u t . html ’
})
)

34. Introduction Forms Authentication Generic Views Caching Others Admin
Object based generic views

35. Introduction Forms Authentication Generic Views Caching Others Admin
Display objects and their lists
from d j a n g o . v i e w s . g e n e r i c . l i s t d e t a i l import
object detail , object list
u r l ( ( r ’ ˆ o b j e c t s / page ( ? P<page >[0 −9]+)/ $ ’ ,
object list ,
dict ( info dict )) ,
( r ’ ˆ o b j e c t s / ( ?P<i d >[0 −9]+)/ $ ’ ,
object detail ,
dict ( info dict )) ,
)

36. Introduction Forms Authentication Generic Views Caching Others Admin
List of generic views
django . views . g e n e r i c . simple . d i r e c t t o t e m p l a t e
django . views . g e n e r i c . simple . r e d i r e c t t o
django . views . g e n e r i c . l i s t d e t a i l . o b j e c t l i s t
django . views . g e n e r i c . l i s t d e t a i l . o b j e c t d e t a i l
django . views . g e n e r i c . create update . c r e a t e o b j e c t
django . views . g e n e r i c . create update . update object
django . views . g e n e r i c . create update . d e l e t e o b j e c t

37. ”Normalized data is for sissies” - Cal Henderson

38. Introduction Forms Authentication Generic Views Caching Others Admin
Different blocks need different caching durations

39. Introduction Forms Authentication Generic Views Caching Others Admin
Generally Memcache Every page
CACHE BACKEND = ’ memcached : / / 1 2 7 . 0 . 0 . 1 : 1 1 2 1 1 / ’
CACHE BACKEND = ’ memcached : / / 1 7 2 . 1 9 . 2 6 . 2 4 0 : 1 1 2 1 1 ;
172.19.26.242:11212;172.19.26.244:11213/ ’

40. Introduction Forms Authentication Generic Views Caching Others Admin
Implement a caching decorator
from d j a n g o . c o r e . c a c h e import c a c h e
def c a c h e f o r ( s e c o n d s , f e t c h =0):
def c a c h e i t ( f u n c ) :
def d e c o f u n c ( s e l f ) :
v a l = cache . get ( s e l f . g e t c a c h e k e y ( f e t c h ))
i f not v a l :
val = func ( s e l f )
cache . s e t ( s e l f . g e t c a c h e k e y ( f e t c h ) ,
val , seconds )
return v a l
return deco func
return c a c h e i t

41. Introduction Forms Authentication Generic Views Caching Others Admin
Apply on the blocks
class TwitterBlock ( TwitterSearchBlock ) :
t e m p l a t e n a m e = ’ t w i t t e r u s e r b l o c k . html ’
a j a x t e m p l a t e = ’ t w e e t s u s e r . html ’
@ c a c h e f o r ( 6 0 ∗ 6 0 , f e t c h =1)
def f e t c h d a t a ( s e l f ) :
tw = T w i t t e r ( e m a i l= ’ 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 (
s c r e e n n a m e= s e l f . d a t a )
r e t u r n u s e r t w e e t s , None

42. Introduction Forms Authentication Generic Views Caching Others Admin
Different cache Backends
• Database
• File System
• Local Memory
• Dummy- For Development

43. Introduction Forms Authentication Generic Views Caching Others Admin
More Paradigms
• Internationalization
• Localization
• Humanization
• CSRF Protection
• Pagination
• Sorting
• Data grid
• Sorl Thumbnail

45. Introduction Forms Authentication Generic Views Caching Others Admin
Admin by models alone

46. Introduction Forms Authentication Generic Views Caching Others Admin
Admin Syntax
from d j a n g o . c o n t r i b import admin
from m o d e l s 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 ’ , ’ datetime ’ )
c l a s s CommentAdmin ( admin . ModelAdmin ) :
l i s t d i s p l a y = ( ’ text ’ ,)
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 )

47. List Page

48. Add an Entry

49. Auto Validation