I am trying to address this as I understand the concept. So, in case this not what you had in mind, feel free to point out. Firstly, I would shoot straight to the basic difference.
Node.js is an event loop that is set from start to be async. It's written in low level in C/C++ and wrapped around JS companions. Node runs on Chrome V8 engine, which allows it to achieve fast performance and features .
Example:
app.use('/', function( req, res ) {
doSomething(req,res,next()) ;
doSomethingAgain(req,res,next()) ;
doFinale();
});
I would only speculate on the python event loop(twisted style), as I haven't had much exposure to its style, but python is very flexible and allows extensibility. So, if you are starting out, either node or python is fine