PyEPL (the Python Experiment-Programming Library) is a versatile, high-level library for coding psychology experiments in Python. If you run human experiments and like coding, then I’d recommend it strongly.
PyEPL’s adoption and utility would both receive a tremendous boost if there were a wider array of snippets and tutorials floating around, so I created a collaborative PyEPL blog to provide an unofficial home for such tutorials, snippets and discussion. See the announcement post for more info.
N.B. I wouldn’t recommend PyEPL in its current form for low-level vision experiments, and it only runs on Mac and Linux. Both these concerns are slowly being addressed though, so things may have changed since the time of writing.