Converting existing module/objects to threads

[jdlists at gmail.com]

I have inheirted some existing code, that i will explain in a moment,
have needed to extend and ultimately should be able to run in threads.
I've done a bunch of work with python but very little with threads and
am looking for some pointers on how to implement, and if the lower
level modules/objects need to be rewritten to use threading.local for
all local variables.

I have a module that communicates with a hardware device, which reads
data off of sensors, that can only talk with one controller at a time.
The controller (my module) needs to (in its simplest form) init,
configure the device, request data, and write out xml, sleep, repeat.

The new request is that the device needs to be queried until a
condition is true, and then start requesting data.  So an instance of a
controller needs to be deadicated to a hardware device forever, or
until the program ends....which ever comes first.

This currently works in a non-threaded version, but only for one device
at a time, there is a need to create a single windows(yeach) service
that talks to many of these devices at once.  I don't need worker
threads that handle seperate portions of the entire job, i need a
single application to spawn multiple processes to run through the
entire communication from configure to report, sleep until the next
interval time and run again.  The communication could last from 1
minute to 10 minutes before it ends.


  Here is the code layout in pseudocode.

module.Object - controller.Main - handles all socket communications

class subcontroller(controller.Main):
  def __init__(self,id,configurationFile):
   controller.Main.__init__(self)
   // instantiate variables and local objects that handle
configuration, logic and data output

  def configure(self,configurationFile):
    //read configurationFile and configure device

  def process(self):
    while 1:
      //based on configuration file, query the device until condition
is true and then write xml, sleep until time to repeat and run again.

within controller there are 5 objects and subcontroller is a sinlge
object that loads other objects from the inherited controller.System

I'm trying to figure out how difficult it is going to be to convert
this to a threaded application.  The original controller.Main is built
to talk to devices in series, never in parallel. so no objects are
considered to be thread safe, but no instance of any of the objects
should need to share resources with any other instance of teh same
object.  they would all have unique configuration files and talk to
devices on unique ip/ports.

on a unix system, forking,while potentially not optimal, would be a
fine solution, unfortunantely this needs to run on windows.

I know i have left out many details, but hopefully this is enough to at
least enable some kind soles to lend an opinnion or two.

many thanks
jd