@asvetlov The idea of the new flag is to disable any subsequent waiting for futures after ThreadPoolExecutor.shutdown(wait=False) returns.

Currently the additional waiting is implemented using "atexit", so I assumed it referred to process exit. (The documentation at https://docs.python.org/3/library/atexit.html doesn't seem to specify precisely when the callbacks are executed.) But looking at the implementation of atexit, it seems that the atexit callbacks are actually called from Py_FinalizeEx.

I think wait_at_exit is descriptive because in most cases the process exit and interpreter shutdown will correlate, but I can still update the docs to make it clearer what "exit" refers to. We should just avoid the word "shutdown" in the flag name to avoid confusion with executor shutdown.