[Twisted-Python] Looking for a simple file event driven loop using Twisted

Hello, I'm looking for some example code I can use to build an app from. I need to 'wait' or sleep for new data in a file. Then wake and process the data. The file is a regular file, not a pipe. It is the output of a existing program (i.e., not mine to modify). Needless to say, the API for hugh. I'm need some help finding the right tools. Thanks, Steven Howe