That was a really interesting introduction. I hadn't looked at Rust before and that gave me a good feel for it. Thanks for putting it together, Armin.

A minor peeve of mine is examples between languages that differ in ways that are unimportant (though maybe it can just justified as "idiomatic code"). It adds bias to the demonstration.

We could have written the python one like the following to wrap the lock up with the results structure (and get the automatic sorting behaviour, too):

    import queue
    from threading import Thread
    
    def fib(num):
        return 1 if num < 2 else fib(num - 2) + fib(num - 1)
    
    def thread_prog(results, i):
        rv = fib(i)
        results.put((i, rv))
    
    def main():
        results = queue.PriorityQueue()
        threads = [Thread(target=thread_prog, args=(results, i)) for i in range(35)]
        [t.start() for t in threads]
        [t.join() for t in threads]
        while not results.empty():
            i, rv = results.get()
            print("fib({}) = {}".format(i, rv))

Though, I've also taken other liberties to make it shorter. I normally stay away from threading in python because the GIL makes it a bit of a waste of time in most cases, and who needs the complexity in their lives?

Again, thanks for the overview, I enjoyed it.