cron with sched module

[Gilles Lenfant]

I'm trying hardly to make a python "cron" like utility that may run
functions/methods periodically (say every x seconds) and predetermined
hours.

I can't use Window "AT" or Unix "cron" cause some functions/methods must be
executed evry 15 seconds. Launching Python executable periodically such a
manner will eat the disk I/O and

So, I'm trying with the "sched" module to do this but I can't add  "enter"
to a scheduler object already running.
So, what's the workaround ?
Use directly lower level "threading" module in lace of sched ?

TIA

Gilles Lenfant