This document summarizes some new features in Django 1.1, including aggregates, F() expressions, model improvements, admin improvements, and generic comment moderation. Aggregates allow querying summary data for entire queries or per row. F() expressions allow atomic database operations like incrementing fields. Models gained unmanaged and proxy models. The admin gained custom actions and list_editable. Comment moderation was added to Django's contrib.

1. Django 1.1
a tour of (some) new features
Idan Gazit
PyWeb-IL, August 31st 2009

3. bit.ly/django11
release notes are your friend

4. omg i haz to rewrite mai code?

5. No!
code you wrote
for 1.0 should
“Just Work”
http://bit.ly/djangoapi

6. With a few exceptions…

7. With a few exceptions…
constraint names on 64-bit platforms

8. With a few exceptions…
constraint names on 64-bit platforms
transactions in tests

9. With a few exceptions…
constraint names on 64-bit platforms
transactions in tests
SetRemoteAddrFromForwardedFor middleware

10. With a few exceptions…
constraint names on 64-bit platforms
transactions in tests
SetRemoteAddrFromForwardedFor middleware
saving of model formsets

11. With a few exceptions…
constraint names on 64-bit platforms
transactions in tests
SetRemoteAddrFromForwardedFor middleware
saving of model formsets
names of uploaded files

12. Also…
changed admin autodiscovery
if your urlconf contains:
(r'^admin/(.*)', admin.site.root),
change it to be:
(r'^admin/', include(admin.site.urls)),

13. bit.ly/django11
release notes are your friend

14. 1.1 new features
1290 tasty commits, 1200 bugs squashed

15. 1.1 new features
10k new lines of documentation

16. That’s a lot of new code.
(at least there’s a lot of new docs)

17. New Features!
not an exhaustive list.

18. • Aggregates
• F() Expressions
• Model improvements
• Admin improvements
• Comment Moderation

19. OM
GW
• Aggregates TF
BB
• F() Expressions Q!
!
• Model improvements
• Admin improvements
• Comment Moderation

20. Aggregates

21. What are aggregates?
• aggregate()
summary for entire query
• annotate()
summary per row returned

22. Aggregate Examples
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
What is the average age for all people?
>>> Person.objects.aggregate(Avg(‘age’))
{‘age__avg’: 23.65}

23. Aggregate Examples
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
What is the average age for all people?
>>> Person.objects.aggregate(Avg(‘age’), Min(‘age’),
Max(‘age’))
{‘age__avg’: 23.65, ‘age__min’: 14, ‘age__max’:87}

24. Aggregate Examples
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
What is the average age for all people?
>>> Person.objects.aggregate(Avg(‘age’), Min(‘age’),
Max(‘age’))
{‘age__avg’: 23.65, ‘age__min’: 14, ‘age__max’:87}
No Chaining!

25. Aggregation functions
• Avg(field): average of field
• Min(field): min of field
• Max(field): max of field
• Sum(field): sum of all values in the field
• Count(field, distinct): num of related objects via field
• StdDev(field, sample)
• Variance(field, sample)

26. Annotation
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
People ordered by number of purchases made
q = Person.objects.annotate(Count(‘purchases’)).order_by(
‘-purchases__count’)
>>> q[0]
<Person: Material Girl>
>>> q[0].purchases__count
4592810191

27. Annotation
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
People ordered by number of purchases made
q = Person.objects.annotate(num_purchases=Count(‘purchases’))
.order_by(‘-num_purchases’)
>>> q[0]
<Person: Material Girl>
>>> q[0].num_purchases
4592810191

28. Annotation
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
Which people have <=10 purchases?
q = Person.objects.annotate(
num_purchases=Count(‘purchases’)).filter(num_purchases__lte=10)

29. Annotation
Person Purchases
first_name CharField thing CharField
last_name CharField price DecimalField
age IntField person FK
Annotations work across JOINs:
What is the average purchase price for
purchases made by each person?
Person.objects.annotate(min_price=Min(‘purchases__price’))

30. Dizzy Yet?
many possibilities

31. Annotation
Order is important!
foo.filter().annotate() != foo.annotate().filter()

32. F( ) expressions

33. F( ) Expressions
class Stock(models.Model):
symbol = models.CharField()
class TradingDay(models.Model):
stock = models.ForeignKey(Stock, related_name="days")
opening = models.DecimalField()
closing = models.DecimalField()
high = models.DecimalField()
low = models.DecimalField()

34. F( ) Expressions
class Stock(models.Model):
symbol = models.CharField()
class TradingDay(models.Model):
stock = models.ForeignKey(Stock, related_name="days")
opening = models.DecimalField()
closing = models.DecimalField()
high = models.DecimalField()
low = models.DecimalField()
from django.db.models import F
# Closed at least 50% up from open
TradingDay.objects.filter(closing__gte=F('opening') * 1.5)
# All downhill
TradingDay.objects.filter(opening=F('high'))
# Works across JOINs
# Stocks that have days with <10pt loss in value
Stock.objects.filter(days__closing__gte=F('days__opening')-10.0)

35. F( ) Expressions
Atomic DB Increment Operations!
class MyModel():
...
counter = models.IntegerField()
MyModel.objects.filter(id=someid).update(counter=F('counter')+1)

36. Model Improvements

37. Unmanaged Models
• Useful for tables or DB views which
aren’t under Django’s control
• Work like regular models
• No table creation during syncdb,
tests, etc.

38. Unmanaged Models
class MyModel():
...
# some fields which match your existing table's column types
class Meta:
managed = False

39. Proxy Models
I already have a model, and
want to change its python
behavior without changing
the underlying table
structure.

40. Proxy Models
class MyProxy(MyModel):
# no new fields!
# but you can define new managers
objects = SupaDupaProxyManager()
proxy_specific_manager = PonyManager()
class Meta:
proxy = True
ordering = ['not_the_original_ordering_field',]
def my_proxy_method(self):
# ... do something

41. admin improvements

42. Admin Actions

43. Custom Admin Actions
def add_cowbell(modeladmin, request, queryset):
queryset.update(myfield='cowbell!')

44. Custom Admin Actions
def add_cowbell(modeladmin, request, queryset):
queryset.update(myfield='cowbell!')
add_cowbell.short_description = "More Cowbell!"

45. Custom Admin Actions
def add_cowbell(modeladmin, request, queryset):
for obj in queryset:
obj.myfield += 'cowbell!'
obj.save()
add_cowbell.short_description = "More Cowbell!"

46. Custom Admin Actions
def add_cowbell(modeladmin, request, queryset):
for obj in queryset:
obj.myfield += 'cowbell!'
obj.save()
add_cowbell.short_description = "More Cowbell!"
class MusicAdmin(admin.ModelAdmin):
list_display = ['artist', 'song']
ordering = ['artist',]
actions = [add_cowbell]

47. list_editable

48. Generic Comment Moderation

49. django.contrib.comments.
moderation
class BlogPost(models.Model):
title = models.CharField()
body = models.TextField()
posted = models.DateTimeField()
enable_comments = models.BooleanField()
is_public = models.BooleanField()

50. django.contrib.comments.
moderation
class BlogPost(models.Model):
title = models.CharField()
body = models.TextField()
posted = models.DateTimeField()
enable_comments = models.BooleanField()
is_public = models.BooleanField()
class BlogPostModerator(moderation.Moderator):
email_notification = True
enable_field = 'enable_comments'
auto_close_field = 'posted'
close_after = 14
moderation.moderator.register(BlogPost, BlogPostModerator)

51. django.contrib.comments.
moderation
class BlogPostModerator(moderation.Moderator):
email_notification = True
enable_field = 'enable_comments'
auto_close_field = 'posted'
close_after = 14
def allow(comment, content_object, request):
# return False to delete comment
def moderate(comment, content_object, request):
# return True to moderate comment
moderation.moderator.register(BlogPost, BlogPostModerator)

52. Random

53. URL Namespaces
(r'^myapp/', include('myapp.urls', namespace='foo', app_name='bar'))
reverse(‘bar:mynamedurl’, args=[‘xyzzy’], current_app=‘foo’)

54. For/Empty template tag
{% for foo in bars %}
<p>{{ foo.name }}</p>
{% empty %}
<p class="empty">No foos in bars!</p>
{% endfor %}

55. More Random!
• forms: hidden_fields() / visible_fields()
• auth using REMOTE_USER:
IIS/mod_auth_sspi, mod_authnz_ldap, etc
• safeseq template filter
like safe but for lists
• django.shortcuts.redirect() view:
def my_view(request):
...
return redirect('some-view-name', foo='bar')

56. Many More!

57. Fin.
@idangazit
idan@pixane.com

58. Photo Credits
• http://www.flickr.com/photos/josstyk/248920216/
• http://www.flickr.com/photos/mar00ned/3274556235/
• http://www.flickr.com/photos/ilumb/361819506/
• http://www.flickr.com/photos/womanofscorn/9163061/
• http://www.flickr.com/photos/ginnerobot/2549674296/
• http://www.flickr.com/photos/squaregraph/24869936
• http://www.flickr.com/photos/aresauburnphotos/3381681226
• http://www.flickr.com/photos/lwr/105783846/
• http://www.flickr.com/photos/jurvetson/447302275
• http://www.flickr.com/photos/leecullivan/240389468
• http://www.flickr.com/photos/pulpolux/3698819113