Here's the Python equivalent, for what it's worth: http://www.trinhhaianh.com/stream.py/

I've been playing around with this in my current project, yet I'm not convinced this is always such a great model. It requires a lot of mental work to remember what types you are operating on at each state in the pipeline. That being said, I'm a big fan of LINQ, and I'd like to see this model applied more frequently to DB queries.