How to create a timer/scheduler in Python?

[John Dann]

I need what I'd call (in .Net) a timer, ie I need to run a function eg
every 2 seconds - it doesn't need to be millisec accurate but it would
be nice if it wasn't eg every 4 seconds or something.

Rather surprisingly, Core Python (Chun) doesn't seem to index 'timer'
or 'scheduler', which leaves me wondering whether this is an aspect of
Python that isn't perhaps widely used?

Looking around on the net I can see references to a thread timer, but
I'm not really looking to start any new threads (I just want part of
the GUI to update every 2 secs) and don't want to get into that sort
of complication while still just learning Python.

Is there really no simple timer/scheduler function available in
Python?