the front end and end-user data-collection we want to build in RoR since it's just some simple forms connected to a database.
The integration with other external api's such as twitter and facebook and parsing of the data entered by the users we want to do in python, mostly because the developer for that part knows python.
Is that possible?
It sounds like the only place the two parts will interact is the database: the RoR parts collect data from the user, the python parts collect data from Twitter and elsewhere.
As long as your database is supported by both languages, there's no a priori reason why this wouldn't work.
Even if you end up needing the two parts to interact more directly, there are plenty of ways of providing an API in one part of the app that the other parts of the app can use regardless of what language they're written in - for instance, it should be easy to have the RoR parts provide a nice RESTful API, and have the python parts interact through that.
If you're going to have different parts of the app developed by different teams, they're going to need a strong interface contract in order to make their parts work together anyway; having that contract be in the form of a RESTful API just makes the parts even more modular and gives you more freedom in the future.
Yes, it is possible at some degree using Java. You may use JRuby and Jython in the same app.
If you're parsing data with python, presumably it's going be put into a database. As long as this is the case you can just run two apps standalone. Saying that, using one language and framework is a better solution, especially when you think that you won't be able reuse any code between the two applications if they are written in two different languages.
Also I know Ruby has good libraries to do all of what is mentioned in your post, as I'm sure Python also does, so there seems little advantage in using the two together.
