python subprocess Popen readline() 会卡住，请帮帮我

Question

我用

Popen

来执行一个字符串

cmd

。

cmd

使用 ascp 发送文件。想用

readline()

读取发送进度的百分比，但是每次都会卡在

readline

中

import subprocess

cmd = "ascp xxxxxxxxx xxxxxxx"

ps = subprocess.Popen(cmd.split(), stdout=subprocess.PIPE, stderror=subprocess.PIPE)

while ps.poll() is None():
    line = ps.stdout.readline()    # I can not get output during transfer, it will stuck here 
    print(line)

ps.wait()