return 的 ThreadPoolExecutor 到任务数组

Question

下面是我从 https://tutorialedge.net/python/concurrency/python-threadpoolexecutor-tutorial/

获得的示例代码

from concurrent.futures import ThreadPoolExecutor
import threading
import random

taskarr = []

def task(n,c):
    print("Executing our Task = {} and {}".format(n,c))
    print("Task Executed {}".format(threading.current_thread()))

def main():
    executor = ThreadPoolExecutor(max_workers=3)
    task1 = executor.submit(task(1,'A'))
    task2 = executor.submit(task(2,'B'))

if __name__ == '__main__':
    main()

在此，如果 executor.submit 被 returned 到简单变量 task1，它就可以工作。但是我的要求是 return 它到一个数组。所以当我这样做的时候 taskarr[0] = executor.submit(任务(1,'A')) 它抛出错误，

TypeError: 'function' object does not support item assignment

Answer 1

我无法复制你的TypeError；显然你还有一些你没有给我们看的代码。正如 rocksportrocker 在他们的中指出的那样，您不能将值分配给尚不存在的索引，就像您尝试将 return 从 executor.submit() 分配给索引 0 一样空列表 typearr。这将提高提到的 IndexError.

但是，我可以生成一些 TypeError，这是因为您错误地调用了 submit。

Executor documentation 将参数 fn 定义为可调用对象，例如一个功能。现在，当您像这样调用 submit 时：

executor.submit(task(1,'A'))

task(1,'A') 在您的主线程中执行，然后将其 return 值（在您的情况下为 None）传递给池线程。池线程然后尝试执行 None(1, 'A') 并引发一个 TypeError: 'NoneType' object is not callable，您看不到它，因为它是在将来包装的。如果你调用 task1.result().

你会看到它

这意味着，执行任务的是您的主线程，而不是您的池线程，正如您在 task:

中的第二条打印语句中应该看到的那样

Task Executed <_MainThread(MainThread, started 11064)>

为了让池线程完成工作，您需要将函数对象 task 传递给 executor.submit，如下所示：

taskarr = []

def task(n,c):
    print("Executing our Task = {} and {}".format(n,c))
    time.sleep(3)  # added this to make sure that two different threads from the pool get a task
    print("Task Executed {}".format(threading.current_thread()))

def main():
    executor = ThreadPoolExecutor(max_workers=3)
    taskarr.append(executor.submit(task, 1,'A'))
    taskarr.append(executor.submit(task, 2,'B'))
    # to show that the main thread continues to execute
    # while the pool threads work on the tasks
    print("{}: tasks submitted".format(threading.current_thread().name))

if __name__ == '__main__':
    main()

输出：

Executing our Task = 1 and A
Executing our Task = 2 and B
MainThread: tasks submitted
Task Executed <Thread(ThreadPoolExecutor-0_0, started daemon 12192)>
Task Executed <Thread(ThreadPoolExecutor-0_1, started daemon 11800)>

return 的 ThreadPoolExecutor 到任务数组

return of ThreadPoolExecutor to array of tasks

python

threadpoolexecutor