The file reading code is a bit of a mess. The file format is somewhat similar to JSON though, so using a dedicated library for that might be better. Then it's just a matter of making some small Python script to convert the old file type.
There's also some sort of network version of the file format. I feel like just using JSON (or at least the same format) there as well is the best idea. Or maybe just get rid of the networking since it's not of great benefit.