如何在线程完成时从线程中获取结果？

Question

以下代码启动了几个线程，并在它们都完成后打印结果：

import threading

results = [None] * 5
threads = [None] * 5

def worker(i):
    results[i] = i

for i in range(5):
    threads[i] = threading.Thread(target=worker, args=(i,))
    threads[i].start()

# here I would like to use the results of the threads which are finished
# while others still run

for i in range(5):
    threads[i].join()

# here I have the results but only when all threads are done
print(results)

正如代码中提到的，我想使用已完成的线程的结果，而其他线程仍在运行。 正确的做法是什么？

我是否应该简单地启动一个具有while True: 循环的新线程并不断检查results 中的新条目，或者是否有此类操作的内置机制（作为threading.Thread 调用的一部分线程完成时会指向回调）？

Answer 1

由于您使用的是 Python 3，concurrent.futures 比 threading 更适合：

import concurrent.futures

results = [None] * 5

def worker(i):
    results[i] = i

with concurrent.futures.ThreadPoolExecutor(5) as pool:
    futmap = {pool.submit(worker, i): i for i in range(len(results))}
    for fut in concurrent.futures.as_completed(futmap):
        print("doing more stuff with", futmap[fut])