（1）本质核心是多进程里执行os.system("wget filename")，开17个进程的进程池意味着同时在下载17个文件。

（2）将指令全部放列表needgfsfile里面。

python
import datetime
import multiprocessing
import os
def downloadgfs(filename):
    os.system(filename)
start_hour = 12
yesterday = (datetime.datetime.now() - datetime.timedelta(days=1)).replace(hour=start_hour, microsecond=0)
ymdstr = f"{str(yesterday.year).zfill(4)}{str(yesterday.month).zfill(2)}{str(yesterday.day).zfill(2)}{str(start_hour).zfill(2)}"
if not os.path.exists(ymdstr):
    os.mkdir(ymdstr)
needgfsfile = [
    f"wget ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gfs.{ymdstr[:-2]}/{ymdstr[-2:]}/atmos/gfs.t{ymdstr[-2:]}z.pgrb2.0p50.f{str(i * 24).zfill(3)} -P {ymdstr}/"
    for i in range(17)]
p = multiprocessing.Pool(processes=17)  # 进to程池
_ = [p.apply_async(func=downloadgfs, args=(i,)) for i in needgfsfile]
p.close()
p.join()