I have a new book out titled Learn Python Visually – Creative Coding with Processing.py. The book contains a refined and redesigned version of what I’ve provided online, printed in full colour with new chapters and nice margins to scrawl in. You can order a copy from the No Starch website or Amazon.
The functions chapter is available as a free sample download here:
I’ll finish off the remaining lessons (listed below), but cannot say exactly when. You can visit from time to time to check for updates, or subscribe via RSS. My thanks go to Åke Jonsson for his feedback on the lessons I’ve posted up to this point.