Using candygram you can send the sync thread a message telling it to reread the config file or you could send a message that changes the setting directly. Candygram is much better than the standard threading module which is designed after the Java threading library. Java recently added another threading library because the old one was not adequate.
The reason you can't simply share a global variable is that threads do not share state. You have to go through a lot of trouble to share that state. First you have to setup some form of interprocess communications such as a memory mapped file, shared mem, pipe, socket etc. You then have to implement locking and try to debug what you have done. Debugging multi threaded programs is inherently difficult. I would highly recommend using candygram or an asynchronous library, since it sounds like you haven't done any multi-threaded programming before. In candygram you can send threads messages which don't require any synchronization or IPC setup. -- http://mail.python.org/mailman/listinfo/python-list