在调用的进程仍在运行时使用python读取命令行输出[重复]

Question

似乎有很多方法可以使用 python 通过命令行调用某些系统进程，然后在进程完成后读取输出。例如，subprocess 模块可以通过subprocess.Popen(['ls']) 完成此操作。

有没有办法在命令仍在运行时读取其输出？

例如，如果我调用 python 脚本multiply.py:

import time

def multiply(a,b):
    newA = a
    newB = b
    while True: #endless loop
        newA = newA+1
        newB = newB+1

        product = newA * newB
        print 'Product: ',product
        time.sleep(1)


multiply(40,2)

使用类似于subprocess.Popen(['python', 'multiply.py]) 的东西，有没有办法

1. 启动进程
2. 在进程运行时静默/主动捕获所有输出
3. 'jump in'随时查看整个输出的内容？

上面的 python 脚本是我对捕获输出感兴趣的那种过程的模型，即有一个无限循环，它每秒打印一个输出；我对主动监控/捕获感兴趣的是这个输出。

Answer 1

这是一个在另一个线程上打开进程的实现（因此您不必阻塞主线程）并使用Queue 与回行通信。使用Event 按需终止线程：

#!/usr/bin/env python

from subprocess import Popen, PIPE
from threading import Thread, Event
from Queue import Queue
from time import sleep

# communicates output lines from process to main thread
lines = Queue()
# kills thread
kill = Event()


def runner():
    p = Popen(["python", "multiply.py"], stdout=PIPE)
    # to get stream behaviour
    while p.poll() is None and not kill.isSet():
        lines.put(p.stdout.readline())

    p.kill()
    # in your use case this is redundant unless the process
    # is terminated externally - because your process is never done
    # after process finished some lines may have been missed
    if not kill.isSet():
        for line in p.stdout.readlines():
            lines.put(line)

# open process on another thread    
t = Thread(target=runner)
t.start()

# do stuff - lines aggregated on the queue    
print "First run"
sleep(1)
while not lines.empty():
    print lines.get()

# move to more important stuff...
sleep(3)

# now check the output we missed
print "Second run"
while not lines.empty():
    print lines.get()

# done doing stuff

# tell thread to kill itself
kill.set()
# wait for thread
t.join()
print "done"