解决了！

以下是screenshot.py 的修改后的代码.通过 py2exe 运行它.

Below are the modified code for screenshot.py. Run it via py2exe.

from multiprocessing import Process, freeze_support
from PIL import Image
import pyscreenshot as ImageGrab
import time

time.sleep(3)


save_dir = "C:/Users/ling/Downloads/test/"

def grab():
    im = ImageGrab.grab()
    im.save(save_dir + "screenshot.png")

if __name__ == "__main__":
    freeze_support()
    p = Process(target=grab)
    p.start()

事实证明，我需要从 multiprocessing 中包含 freeze_support 和 Process

It turned out that I need to include freeze_support and Process from multiprocessing