python 使用Pool，并需要关注结果

import multiprocessingimport timedef func(msg):    for i in xrange(3):    print msg    time.sleep(1)    return "done " + msgif __name__ == "__main__":    pool = multiprocessing.Pool(processes=4)    result = []    for i in xrange(10):        msg = "hello %d" %(i)        result.append(pool.apply_async(func, (msg, )))    pool.close()    pool.join()    for res in result:        print res.get()    print "Sub-process(es) done."