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: 
In general, I think you'll find [web2py](http://www.web2py.com) to be one of the easiest frameworks to set up, learn, and use. web2py makes it very easy to [generate JSON](http://web2py.com/book/default/chapter/09#HTML,-XML,-and-JSON) (just add a .json extension), and it now includes new functionality to automatically create [RESTful web services](http://web2py.com/book/default/chapter/09#RESTful-Web-Services) to access database models. In particular, check out the [parse\_as\_rest](http://web2py.com/book/default/chapter/09#parse_as_rest-(experimental)) and [smart\_query](http://web2py.com/book/default/chapter/09#smart_query-(experimental)) functionality.

If you need any help, ask on the [mailing list](https://groups.google.com/forum/?fromgroups#!forum/web2py).
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.