Question: I need to create a Python REST/JSON web service for an iOS app to interact with. There will be no front end on the web.

What will be the fastest, most lightweight framework to use for this? Learning curve to implement also considered?

From the research I've done Django-Tastypie or Djanjo-Piston look like the best options, with Tastypie winning because the codebase is being maintained actively?

Answer: 
Take a look to [flask](http://flask.pocoo.org/) and its extension [flask-restful](http://flask-restful.readthedocs.org/en/latest/index.html)

```
from flask import Flask
from flask.ext import restful

app = Flask(__name__)
api = restful.Api(app)

class HelloWorld(restful.Resource):
    def get(self):
        return {'hello': 'world'}

api.add_resource(HelloWorld, '/')

if __name__ == '__main__':
    app.run(debug=True)

```
You might also want to check out [Parse](https://www.parse.com/). They are free to use right now, and will give you a nice [REST API](https://www.parse.com/docs/rest) for you mobile apps. 

However, as @iksnar points out, you don't write anything in Python, or anything at all for the backend. If you need to have the backend running in Python on your own servers I am a big fan of TastyPie if you are using Django already and the Django ORM already.