python的線程池使用

from concurrent.futures import ThreadPoolExecutor
import time


def say_hello(a, s):
    print("hello: "+a)
    print(s)
    time.sleep(4)
    return {"code": 111}


def main():
    seed=["a","b","c", "d"]
    start2=time.time()
    future = {}
    # 創建包含3個線程的線程池
    executor = ThreadPoolExecutor(3)
    for each in seed:
        # 提交任務到線程池
        a = executor.submit(say_hello, each, 4)
        # 保存提交後返回的對象用來查詢結果(A Future representing the given call)
        future[each] = a
    # shutdown用來保證不會在向線程池中新增任務,其內參數爲False表示不會等待線程池內任務結束,直接返回(常用於不需要返回結果時),參數爲True時(默認爲True),會等待線程池內任務執行完畢纔會繼續向下走
    executor.shutdown(False)
    # 當使用future["a"].result()時,無論shutdown內參數是True還是False,都會阻塞至直到該任務執行完.
    # result()內的數字爲超時時間,單位是s,默認值爲None,無超時時間
    print(future["a"].result(5))
    end2=time.time()
    print("time2: "+str(end2-start2))
    return


if __name__ == '__main__':
    main()