when x process isn't running... do something

[Bart Nessux]

Howdy,

I'm trying to time how long it takes dd to run on a G5, versus how long 
it takes to run on a G4 (PATA vs. SATA). Both sytems have Mac OS X 
10.3.2 and Python 2.3. Could someone demonstrate how I might use Python 
to monitor for the presense of a process and to do something (in this 
case send an email which I know how to do) as soon as that process is no 
longer present? Any suggestions on how to monitor? Call top every 5 secs 
and read it's output searching for 'dd'???

TIA,
Bart