I had a squint at the ThreadPoolExecutor code on github and it uses the default parameters. Exactly how many threads you get depends on which version of python

I had a squint at the ThreadPoolExecutor code on github and it uses the default parameters. Exactly how many threads you get depends on which version of python you are running: > Changed in version 3.5: If max_workers is None or not given, it will default to the number of processors on the machine, multiplied by 5, assuming that ThreadPoolExecutor is often used to overlap I/O instead of CPU work and the number of workers should be higher than the number of workers for ProcessPoolExecutor. Not knowing how many things are happening in parallel means it is difficult to draw conclusions from it.