如何从python中的多线程获取返回值

Question

我要获取多线程程序的返回值，我们有它的队列，

代码：

#!/usr/bin/python3.6
from queue import Queue
from threading import Thread

class Worker(Thread):
 def __init__(self, tasks):
    Thread.__init__(self)
    self.tasks = tasks
    self.daemon = True
    self.start()
 def run(self):
    while True:
        func, args, kargs = self.tasks.get(True, None)
        if not func:
            break
        try:
            func(*args, **kargs)
        except Exception as e:
            # print e
            pass
        self.tasks.task_done()
class ThreadPool:

  def __init__(self, num_threads):
    self.threads = []
    self.num_threads = num_threads
    self.tasks = Queue(self.num_threads)
    for _ in range(self.num_threads):
        worker = Worker(self.tasks)
        self.threads.append(worker)
  def add_task(self, func, *args, **kargs):
    self.tasks.put((func, args, kargs))

  def wait_completion(self):
    self.tasks.join()
    for _ in range(self.num_threads):
        self.add_task(None, None, None)
    for t in self.threads:
        t.join()
def hello(i):
 print("OK %s " % i)
 if i == 20:
    return i
 else:
    return i
pool = ThreadPool(int(3))
for item in range(1, 10000):
    pool.add_task(hello, item)

pool.wait_completion()

我使用线程1返回值1和线程2返回值2，那么如何获取从多线程返回的值'数字'？