How big are the files and how long does the processing take? How much faster does the processing need to be? How many lines of code in your script?

So far you have told us that you have a small number of files (300-500 files is a small number) that you are either converting to cvs or from cvs (it's not clear which way you are going) and it's taking too long. But that is nothing like enough information for us to actually provide you any useful advice. Perhaps you would like to tell us more about what you are trying to do and why the current processing time is a problem so we have a little more context.