Python - 用于循环完成之前它应该是

Question

我目前正在通过基于for循环长度的线程池执行任务，并且当它不应该（在循环结束之前）结束它的执行。有什么想法吗？这是相关代码：

from classes.scraper import size
from multiprocessing import Pool
import threading

if __name__ == '__main__':
    print("Do something")
    size = size()
    pool = Pool(processes=50)
    with open('size.txt','r') as file:
        asf = file.read()
        for x in range(0,1000000):
            if '{num:06d}'.format(num=x) in asf:
                continue
            else:
                res = pool.apply_async(size.scrape, ('{num:06d}'.format(num=x),))

这是控制台输出（我打印出size.scrape()内的值。

...
...
...
013439
013440
013441
013442
013443

Process finished with exit code 0