UnRESTful APIs with Django

UnRESTful APIs
with Django
Ari Lacenski
@tensory
June 25, 2013
Tuesday, June 25, 13

Why create an API?
API stands for Application Programming Interface.
An API to your project lets people write applications
that use your technology.
Web APIs are collections of URLs pointing to services.

Remote Procedure Call
Uses URL patterns to suggest what you get back
like: yoursite.com/show/articles?article_id=42
Used to be super common, until REST pattern emerged
good luck with that
Often inconsistent &
needs a lot of docs
Response data isn’t
linked to DB records

REST
(REpresentational State Transfer)
Uses HTTP concepts: GET, POST, DELETE & PUT
Super useful, super popular!
Lets you build an API that directly represents the data
that you want developers to work with

REST
GET /article/42 returns JSON representation of article
with id=42
POST /article/ gets back JSON with a saved article ID
GET /article/ gets back a list of article IDs
{ ‘article’: { ‘id’: 42, ‘author’: ‘Becky
Smith’, ‘title’: ‘API Design 101’ }}

REST works great.
“RESTful API” designs try to follow the REST pattern.
There are free API libraries for Python web frameworks.
This all works well for creating APIs to relational data.
BUT WAIT
What if your data is too complex to store in a DB table?

Extend your pattern.
Consider a photo service with some color search tools.
Upload a photo? POST to /upload/ with ﬁle + metadata
Get photo details? GET /photo/
Want to let your API users calculate the average color in
some random images? ... Hmm.

Let’s make it happen.

models.py
from django.db import models
class Photo(models.Model):
uploader = models.ForeignKey(User)
uploaded_at = models.DateTimeField()
file = models.FileField(blank=True, null=True)
How do you turn this model into an API?
Try Tastypie.

from tastypie.resources import Resource
from models import Photo
class PhotoResource(Resource):
class Meta(object):
queryset = Photo.objects.all()
resource_name = ‘photo’
allowed_methods = [‘get’, ‘post’, ‘put’]
api.py

urls.py
from tastypie.api import Api
from api import PhotoResource
photo_api = Api(api_name='api')
urlpatterns = patterns(‘’, include(photo_api.urls))
# ... other routes in your app can go
# into this urlpatterns definition, if you want

Can we upload photos?
Can we get back one photo’s data?
Can we see data about all photos
we’ve uploaded?
Yup.
Sure.
Check it out.
GET /api/photo/42
GET /api/photo/
POST /api/photo/
Where are we now?

But what about that
color method?
id=34
id=60
id=29

1. In api.py, add a method to your API’s
PhotoResource.
2. In views.py, create any helper methods you need
for your Photo model.
3. In api.py, use prepend_urls to add an RPC URL
pattern for the new PhotoResource method.
Mix in an RPC URL.

import views
from tastypie.resources import Resource
from models import Photo
class PhotoResource(Resource):
class Meta(object):
queryset = Photo.objects.all()
resource_name = ‘photo’
allowed_methods = [‘get’, ‘post’, ‘put’]
def prepend_urls(self):
return [
url(r”^(?P<resource_name>)/average/” %
self._meta.resource_name, self.wrap_view('get_average_color'))
]
def get_average_color(self, request):
photo_ids = request.getlist(‘ids’)
# Add a get_average_color method to your app views.
result = views.get_average_color(photo_ids)
return { ‘color’: result.color_code }
api.py

You’re done!
GET /api/photo/average?ids=34,60,29
{ ‘color’: ‘BAB5B2’ }

Find out more
Comparison of REST vs XML RPC
http://bit.ly/8lkoPK
Django API packages comparison
https://www.djangopackages.com/grids/g/api/
Tastypie
http://django-tastypie.readthedocs.org/
https://github.com/toastdriven/django-tastypie

Thanks for listening!
Ari Lacenski @tensory

UnRESTful APIs with Django

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