I personally do not use the objected oriented approach, mostly because it a) only get in the way; b) you will never reuse that as a module.
but something that is not discussed here, is that you must use threading or multiprocessing. Always. otherwise your application will be awful.
just do a simple test: start a window, and then fetch some URL or anything else. changes are your UI will not be updated while the network request is happening. Meaning, your application window will be broken. depend on the OS you are on, but most times, it will not redraw, anything you drag over the window will be plastered on it, until the process is back to the TK mainloop.