Nice work! I will send you the prize money.

Question:

You create a separate dict for each thread:
results.append({})

And you also lock this dict for every write:

      lock.acquire()
            if operation not in self.stats:
                self.stats[operation] = 1
            else:
                self.stats[operation] += 1
            lock.release()

Is this required since the dict is still part of the results list? I do not know, so this is a genuine question.

My solution is a bit different in that regard and also yields faster times, I will be submitting a tutorial soon.