I have often wanted a timer in Python with the same functions as Javas Timer (http://java.sun.com/javase/6/docs/api/java/util/Timer.html). I want it repeating instead of being just a one-shot thing like Pythons Timer class. 

Here is a patch that adds such a class to the threading module. You then use it like this:

import threading

def hello():
    print "Hi there!"

t = threading.PeriodicTimer(5, hello)
t.start()    # "Hi there!" will be printed every five seconds.

The use cases for this class is things like updating canvases, updating simulations and polling stuff. I can provide documentation and unit test patches if this class is deemed worthy.