First, I second Matt's comment about using a boring old for loop when it is the simplest way to express what you want to do. Being Pythonic is not about using exotic features to scrunch your code down to a cool one-liner. It is about expressing your intentions in a simple, direct way. Sometimes comprehensions, generators, etc. help. Sometimes they only obfuscate.
That said, the *most* Pythonic way to do something is to find the existing library that already does it. Check out the Image.point() function in the PIL documentation. You may not need to convert the image to a list at all. - Roger -- http://mail.python.org/mailman/listinfo/python-list
