I have a log file being written by another process which I want to watch for changes. Each time a change occurs I\'d like to read the new data in to do some processing on it
Have you already looked at the documentation available on http://timgolden.me.uk/python/win32_how_do_i/watch_directory_for_changes.html? If you only need it to work under Windows the 2nd example seems to be exactly what you want (if you exchange the path of the directory with one of the files you want to watch).
Otherwise, polling will probably be the only really platform-independent option.
Note: I haven't tried any of these solutions.