如何从python中的线程池获取结果？

Question

我在这里搜索了有关如何在python中进行线程化的信息，但到目前为止，我还没有得到我需要的答案。我对Queue和Threading
python类不是很熟悉，因此，这里给出的一些答案对我来说毫无意义。

我想创建一个线程池，我可以给它执行不同的任务，当所有线程都结束时，获取结果值并处理它们。到目前为止，我已尝试执行此操作，但无法获得结果。我写的代码是：

from threading import Thread
from Queue import Queue

class Worker(Thread):
    """Thread executing tasks from a given tasks queue"""
    def __init__(self, tasks):
        Thread.__init__(self)
        self.tasks = tasks
        self.daemon = True
        self.result = None
        self.start()
    def run(self):
        while True:
            func, args, kargs = self.tasks.get()
            try:
                self.result = func(*args, **kargs)
            except Exception, e:
                print e
            self.tasks.task_done()
    def get_result(self):
        return self.result

class ThreadPool:
    """Pool of threads consuming tasks from a queue"""
    def __init__(self, num_threads):
        self.tasks = Queue(num_threads)
        self.results = []
        for _ in range(num_threads):
            w = Worker(self.tasks)
            self.results.append(w.get_result())
    def add_task(self, func, *args, **kargs):
        """Add a task to the queue"""
        self.tasks.put((func, args, kargs))
    def wait_completion(self):
        """Wait for completion of all the tasks in the queue"""
        self.tasks.join()
    def get_results(self):
        return self.results

def foo(word, number):
    print word*number
    return number

words = ['hello', 'world', 'test', 'word', 'another test']
numbers = [1,2,3,4,5]
pool = ThreadPool(5)
for i in range(0, len(words)):
    pool.add_task(foo, words[i], numbers[i])

pool.wait_completion()
results = pool.get_results()
print results

输出将给定字数的字符串打印给定字数乘以给定数，但结果列表中没有值，因此我应该将func的返回值放在这里。

或简单的方法是创建一个列表，在其中填充队列并添加字典或某个变量以将结果存储为函数的参数，然后将任务添加到队列后，将此结果参数添加到结果列表中：

def foo(word, number, r):
    print word*number
    r[(word,number)] = number
    return number

words = ['hello', 'world', 'test', 'word', 'another test']
numbers = [1,2,3,4,5]
pool = ThreadPool(5)
results = []
for i in range(0, len(words)):
    r = {}
    pool.add_task(foo, words[i], numbers[i], r)
    results.append(r)
print results

Answer 1

Python实际上有一个可以使用的内置线程池，只是没有充分说明：

from multiprocessing.pool import ThreadPool

def foo(word, number):
    print (word * number)
    r[(word,number)] = number
    return number

words = ['hello', 'world', 'test', 'word', 'another test']
numbers = [1,2,3,4,5]
pool = ThreadPool(5)
results = []
for i in range(0, len(words)):
    results.append(pool.apply_async(foo, args=(words[i], numbers[i])))

pool.close()
pool.join()
results = [r.get() for r in results]
print results

或（使用map代替apply_async）：

from multiprocessing.pool import ThreadPool

def foo(word, number):
    print word*number
    return number

def starfoo(args):
    """

    We need this because map only supports calling functions with one arg. 
    We need to pass two args, so we use this little wrapper function to
    expand a zipped list of all our arguments.

    """    
    return foo(*args)

words = ['hello', 'world', 'test', 'word', 'another test']
numbers = [1,2,3,4,5]
pool = ThreadPool(5)
# We need to zip together the two lists because map only supports calling functions
# with one argument. In Python 3.3+, you can use starmap instead.
results = pool.map(starfoo, zip(words, numbers))
print results

pool.close()
pool.join()