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Django's Architecture: The Good, The Bad, and The Ugly
Andrew Godwin
October 22, 2011
Programming
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Django's Architecture: The Good, The Bad, and The Ugly
A talk I gave at FOSDEM 2011.
Andrew Godwin
October 22, 2011
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Transcript
The Good, The Bad, & The Ugly Django's Architecture: Andrew
Godwin FOSDEM 2011
Django core committer Mercenary programmer Startup founder (ep.io)
Django: A Brief History
Initial Public Release in 2005
1.0 in 2008
1.3 in a few weeks
Basic Layout
contrib core db dispatch http forms middleware shortcuts templates views
contrib admin auth comments contenttypes flatpages gis humanize localflavor messages
sessions staticfiles syndication
core cache files handlers mail management serializers servers paginator urlresolvers
validators
db backends models
others views.decorators views.generic csrf test forms.widgets forms.fields forms.formsets forms.models
Almost every piece of code has been changed since 2005
""Good, Bad, Ugly?""
Lessons from both the past and the present
Some stuff here is historical (we fixed it, thankfully)
There's still nasty bits (we're working on those)
The Good
contrib.admin
admin.site.register( Book, list_display = [ "title", "slug", ], prepopulated_fields =
{ "slug": ( "title", "description", ) } )
The Model Layer (sometimes incorrectly called the ORM)
Sensible Abstractions (sessions, caching, mail, etc.)
GeoDjango (contrib.gis)
from django.contrib.gis.db import models class Lakes(models.Model): name = models.CharField(max_length=100) rate
= models.IntegerField() geom = models.MultiPolygonField() objects = models.GeoManager() >>> lake3 = Lakes.objects.get(id=3) >>> newlake.geom.contains(lake3.geom) True
None
Debugging Tools (./manage.py shell, testing tools, culture)
CSRF Protection (the new type)
Auto-escaping
View API simplicity
Python
MultiDB
Small actual core
Documentation (both the core docs and the culture)
The Community
Not being too high-level
The Bad
pre-1.2 CSRF Would you like token leakage with that?
<form action="/someview/" method="POST"> ... </form>
<form action="/someview/" method="POST"> ... <input name="csrftoken" ...></form>
<form action="http://evil.com" method="POST"> ... <input name="csrftoken" ...></form>
Schema changes Add a column? Oh, no, not sure we
can do that.
Template Implementation Hasn't changed that much.
The Ugly
""Magic"" It's hard to define, but you know it when
you see it.
Too many regular expressions They're great until they're 100+ chars
long
(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)* # dot-atom |^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*" # quoted-string )@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?$' # domain (^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*
# dot-atom |^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*" # quoted-string )@(?:[A-Z0-9]+(?:-*[A-Z0-9]+)*\.)+[A-Z]{2,6}$ # domain
Customising Auth Can't really touch it.
{% endifnotequal %} Thankfully we fixed this in 1.2.
Are there lessons to be learnt?
Not everything needs fixing now A lot of these issues
have third-party solutions
How do you get better? Consistency, not always writing new
features, and people with too much free time.
Thanks. Andrew Godwin @andrewgodwin http://aeracode.org