即使队列为空，地图也不会 return

Question

当我的队列为空时，map 方法不会return。

为了完成脚本，我可以使用 treahdpool.map_async 或 tasks.get(block=False)。但我想了解为什么它在完成队列后不解除阻塞threadpool.map()。

from multiprocessing.dummy import Pool as ThreadPool
from queue import Queue

def threadworker(tasks):
    while True:
        # try:
        #     func, args, kargs = tasks.get(block=False)
        # except Empty:
        #     break
        func, args, kargs = tasks.get()
        try:
            func(*args, **kargs)
        except Exception as e:
            print(e)
        finally:
            tasks.task_done()


def wait_delay(d):
    print('sleeping for (%d)sec' % d)
    time.sleep(d)


if __name__ == '__main__':
    tasks = Queue()

    for d in range(1,5):
        tasks.put((wait_delay, (d,), {}))

    threadpool = ThreadPool(processes=2)
    # threadpool.map_async(threadworker, [tasks])
    threadpool.map(threadworker, [tasks]) # blocking...
    tasks.join()

Answer 1

Queue.get() 正在阻塞它只会坐在那里等待得到什么。指定超时并通过中断 while 循环来处理异常。

from queue import Queue,Empty
def threadworker(tasks):
    while True:
        # try:
        #     func, args, kargs = tasks.get(block=False)
        # except Empty:
        #     break
        try:
            func, args, kargs = tasks.get(timeout=5)
        except Empty:
            break
        try:
            func(*args, **kargs)
        except Exception as e:
            print(e)
        finally:
            tasks.task_done()

即使队列为空，地图也不会 return

map does not return even if queue is empty

python

queue

multithreading