Class variables and Multiprocessing(or concurrent.futures.ProcessPoolExecutor)

[snippsat]

I also think you are running into problems with the GIL,

Not the problem here as concurrent.futures ProcessPoolExecutor() bypass the GIL,the problem here is as mention that code dos nothing useful.

ProcessPoolExecutor uses the multiprocessing module, which allows it to side-step the Global Interpreter Lock
but also means that only picklable objects can be executed and returned.