python: concurrent.futures.as_completed所有流程完成后才打印结果

Question

1)我正在尝试使用 concurrentFutures 执行 8 个并行进程。代码按预期工作。但是只有在所有过程完成后才会打印结果。我希望在结果可用时立即打印结果（而不是在所有过程完成之后）。我该怎么做？

2)“do_it”函数在 IDLE 环境中不打印任何内容，只有 main() 函数中的打印命令在 IDLE window 上打印。但是“do_it”中的打印命令正在在线 python 编译器 window (https://www.programiz.com/python-programming/online-compiler/) 上打印。为什么？

我在 Windows OS 上使用 python3.9.5。

import concurrent.futures
import time

def do_it(x):
    print(f'sleeping for {x}')
    start = time.perf_counter()
    time.sleep(x)
    end = time.perf_counter()
    tTaken = round(end - start, 2)
    return ['done sleeping', tTaken]

def main():
    start = time.perf_counter()

    with concurrent.futures.ProcessPoolExecutor() as executor:
        delays = [1,2,3,4,5,6,7,8]
        results = [executor.submit(do_it, x) for x in delays]

    for f in concurrent.futures.as_completed(results):
        [txt, duration] = f.result()
        print(f'{txt} : time taken {duration}')

    end = time.perf_counter()
    tTaken = round(end - start, 2)
    print(f'total time  taken : {tTaken}')
        
    
if __name__ == '__main__':
    main()

Answer 1

您只能在as_completed 执行程序完成后开始。

尝试运行而执行程序仍然存在：

def main():
    start = time.perf_counter()

    print("Submitting jobs")
    with concurrent.futures.ProcessPoolExecutor() as executor:
        delays = [1, 2, 3, 4, 5, 6, 7, 8]
        results = [executor.submit(do_it, x) for x in delays]

        print("Running as_completed", flush=True)
        for f in concurrent.futures.as_completed(results):
            [txt, duration] = f.result()
            print(f"{txt} : time taken {duration}", flush=True)

    end = time.perf_counter()
    tTaken = round(end - start, 2)
    print(f"total time  taken : {tTaken}")

结果应该是这样的：

Submitting jobs
sleeping for 1
sleeping for 2
sleeping for 3
Running as_completed
sleeping for 4
sleeping for 5
done sleeping : time taken 1.04
sleeping for 6
done sleeping : time taken 2.03
sleeping for 7
done sleeping : time taken 3.0
sleeping for 8
done sleeping : time taken 4.01
done sleeping : time taken 5.05
done sleeping : time taken 6.07
done sleeping : time taken 7.01
done sleeping : time taken 8.03
total time  taken : 12.08

编辑

关于子进程丢失的输出，这与 Python 如何在 ms-windows 上启动新进程有关。与 UNIX/POSIX 系统相反，文件句柄 而不是 由子进程继承。因此，您不会在 ms-windows 上看到子进程的 print 输出。猜测，在线python在UNIX/POSIX系统上是运行。

python: concurrent.futures.as_completed所有流程完成后才打印结果

python: concurrent.futures.as_completed printing results only after all the processes are completed

python

concurrent.futures