"RuntimeError: Calling Tcl from different appartment" tkinter and threading
To a very good first and second approximation, the core of Tk is single threaded. It can be used from multiple threads, but only by initialising it separately in each of those threads. Internally, it uses thread-specific variables extensively to avoid the need for major locking (that is, it has nothing like a big Global Interpreter Lock) but that means you must not cheat. Whatever thread initialises a Tk context must be the only thread that interacts with that Tk context. This includes loading the Tkinter module so you are effectively restricted to using Tkinter from your main thread only; working around this is serious expert's-only stuff.
I recommend that you make your worker threads make changes to your GUI by posting events to it using a queue (or otherwise interlock with critical sections and condition variables, though I find queues easier in practice).