UnRESTful APIs with DjangoAri Lacenski@tensoryJune 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.

Tuesday, June 25, 13

Remote Procedure Call

Uses URL patterns to suggest what you get backlike: 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

Tuesday, June 25, 13

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

Tuesday, June 25, 13

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’ }}

Tuesday, June 25, 13

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?

Tuesday, June 25, 13

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.

Tuesday, June 25, 13

Let’s make it happen.

Tuesday, June 25, 13

models.pyfrom 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.

Tuesday, June 25, 13

from tastypie.resources import Resourcefrom models import Photo

class PhotoResource(Resource): class Meta(object): queryset = Photo.objects.all() resource_name = ‘photo’ allowed_methods = [‘get’, ‘post’, ‘put’]

api.py

Tuesday, June 25, 13

urls.pyfrom tastypie.api import Apifrom 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

Tuesday, June 25, 13

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?

Tuesday, June 25, 13

But what about that color method?

id=34id=60

id=29

Tuesday, June 25, 13

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.

Tuesday, June 25, 13

import viewsfrom tastypie.resources import Resourcefrom 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

Tuesday, June 25, 13

You’re done!

GET /api/photo/average?ids=34,60,29

{ ‘color’: ‘BAB5B2’ }

Tuesday, June 25, 13

Find out moreComparison 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

Tuesday, June 25, 13

Thanks for listening!

Ari Lacenski @tensory Tuesday, June 25, 13