Twisted Internet: Asynchronous I/O and Events.
Twisted Internet is a collection of compatible event-loops for Python. It contains the code to dispatch events to interested observers and a portable API so that observers need not care about which event loop is running. Thus, it is possible to use the same code for different loops, from Twisted's basic, yet portable, select-based loop to the loops of various GUI toolkits like GTK+ or Tk.