Python 中的并行程序不产生任何输出

Question

我有一个简单的任务。 需要为大量文件运行特定功能。 这个任务可以很容易地并行化。

这是工作代码：

# filelist is the directory containing two file, a.txt and b.txt.
# a.txt is the first file, b.xt is the second file
# I pass a file that lits the names of the two files to the main program

from concurrent.futures import ProcessPoolExecutor, as_completed
from pathlib import Path
import sys

def translate(filename):
    print(filename)
    f = open(filename, "r")
    g = open(filename + ".x", , "w")
    for line in f:
        g.write(line)

def main(path_to_file_with_list):
    futures = []
    with ProcessPoolExecutor(max_workers=8) as executor:
        for filename in Path(path_to_file_with_list).open():
            executor.submit(translate, "filelist/" + filename)
        for future in as_completed(futures):
            future.result()

if __name__ == "__main__":
     main(sys.argv[1])

但是，不会创建新文件，即该文件夹不包含 a.txt.x 和 b.txt.x 文件。

上面的代码有什么问题，我该如何使它工作？

谢谢。

Answer 1

这应该让你走上正确的道路。 如果它不起作用并且不是一个明显的错误，那么我怀疑您可能没有正确设置所有文件路径...我应该指出，写入文件将受益于线程而不是减少开销的进程。 文件 I/O 应该释放 GIL，这样你就会从加速中受益（如果你一次复制多于一行，效果会显着增加。）也就是说，如果你只是复制文件，你真的应该只使用shutil.copy或shutil.copy2

from concurrent.futures import ProcessPoolExecutor, wait
from pathlib import Path
import sys

def translate(filename):
    print(filename)
    with open(filename, "r") as f, open(filename + ".x", , "w") as g:
        for line in f:
            g.write(line)

def main(path_to_file_with_list):
    futures = []
    with ProcessPoolExecutor(max_workers=8) as executor:
        for filename in Path(path_to_file_with_list).open():
            futures.append(executor.submit(translate, "filelist/" + filename))
        wait(futures) #simplify waiting on processes if you don't need the result.
        for future in futures:
            if future.excpetion() is not None:
                raise future.exception() #ProcessPoolEcecutors swallow exceptions without telling you...
        print("done")

if __name__ == "__main__":
     main(sys.argv[1])