FInding files with python

[Widgeteye]

I'm really new at this programming stuff so please bare
with me.   (:

I'm trying to figure out how you would test for the existence
of a file on your drive in python.

I want to write a little program that does the following:

If (file exists)
  do the following

But I can't figure out how to test for the file..   
help??

Thanks


-- 

"You can always make peace with an F-16 in your pocket"
     -Yitzhak Rabin