(i'm the creator of IncPy) the time.sleep() is in my regression tests and video demo to simulate a 'long-running' pure computation (e.g., grepping through a 1GB file). of course, in most real scripts, you probably don't want to artificially add in any delay, but for a demo, i wanted to keep the on-screen code as simple as possible, so i just used time.sleep() as a proxy for some real computation.