I've installed Python 2.7 to use with RDKit, but I find that any scripts I write hang at 30% when running. However, in the preview window they execute perfectly well. I'm running KNIME 3.2.3, but I don't think that's affecting things here. My python installation is 2.7.2, via Anaconda for Windows.
Just adding the further point to say that in some cases (like starting KNIME up), when i try to run the same script, nothing hapens, and I get an error in the console Execute failed: Could not start python kernel