For this problem the multiple process version would be quite simple in python or any other languages. It's a classic same program multiple data (SPMD) task. You split the file into N chunks than run N versions of the original program on it (a Map). You then need to collate the results, which required a second program, but that step is similar to the sorting step in the original and so would be negligible wrt wall time (a quick Reduce).

For large files you should get almost embarrassing parallelism.