Django 1.1 Tour

Django 1.1
a tour of (some) new features

Idan Gazit
PyWeb-IL, August 31st 2009

bit.ly/django11
release notes are your friend

omg i haz to rewrite mai code?

No!
code you wrote
for 1.0 should
“Just Work”

http://bit.ly/djangoapi

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


transactions in tests



SetRemoteAddrFromForwardedFor middleware




saving of model formsets




saving of model formsets

names of uploaded files

Also…
changed admin autodiscovery

if your urlconf contains:
(r'^admin/(.*)', admin.site.root),

change it to be:
(r'^admin/', include(admin.site.urls)),

1.1 new features

1290 tasty commits, 1200 bugs squashed

1.1 new features

10k new lines of documentation

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

New Features!
not an exhaustive list.

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

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

What are aggregates?

• aggregate()
summary for entire query
• annotate()
summary per row returned

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}

Aggregate Examples
Person Purchases

>>> Person.objects.aggregate(Avg(‘age’), Min(‘age’),
Max(‘age’))
{‘age__avg’: 23.65, ‘age__min’: 14, ‘age__max’:87}

Aggregate Examples
Person Purchases

>>> Person.objects.aggregate(Avg(‘age’), Min(‘age’),
Max(‘age’))
{‘age__avg’: 23.65, ‘age__min’: 14, ‘age__max’:87}

No Chaining!

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)

Annotation
Person Purchases

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

Annotation
Person Purchases

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

Annotation
Person Purchases

Which people have <=10 purchases?
q = Person.objects.annotate(
num_purchases=Count(‘purchases’)).filter(num_purchases__lte=10)

Annotation
Person Purchases

Annotations work across JOINs:
What is the average purchase price for
purchases made by each person?
Person.objects.annotate(min_price=Min(‘purchases__price’))

Annotation

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

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()

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)

F( ) Expressions
Atomic DB Increment Operations!
class MyModel():
...
counter = models.IntegerField()

MyModel.objects.filter(id=someid).update(counter=F('counter')+1)

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.

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

class Meta:
managed = False

Proxy Models

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

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

Custom Admin Actions

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


queryset.update(myfield='cowbell!')

add_cowbell.short_description = "More Cowbell!"


for obj in queryset:
obj.myfield += 'cowbell!'
obj.save()



for obj in queryset:
obj.myfield += 'cowbell!'
obj.save()


class MusicAdmin(admin.ModelAdmin):
list_display = ['artist', 'song']
ordering = ['artist',]
actions = [add_cowbell]

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()

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)

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)

URL Namespaces

(r'^myapp/', include('myapp.urls', namespace='foo', app_name='bar'))

reverse(‘bar:mynamedurl’, args=[‘xyzzy’], current_app=‘foo’)

For/Empty template tag

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

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')

Fin.
@idangazit
idan@pixane.com

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

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