When your existing script is running, what percentage of cpu does top/Program Manager show it is consuming?

Does the system where you are running this program have multiple cpus? If not, is there are multiple cpu system available on which it could be run?

The answers to those questions dictate whether there is any mileage in improving the performance of your script using threads.

It woudl also be much simpler to provide a thread solution, if that is going to be beneficial, if you posted the entire script, along with a few lines showing the format of (each of) the input file(s).