python:非阻塞子进程，检查stdout [英] python: nonblocking subprocess, check stdout

问题描述

好，所以我要解决的问题是这样:

Ok so the problem I'm trying to solve is this:

我需要运行一个设置了一些标志的程序，检查其进度并报告给服务器.因此，我需要我的脚本来避免在程序执行时阻塞，但是我还需要能够读取输出.不幸的是，我认为Popen可用的任何方法都不会读取输出而不会阻塞.我尝试了以下方法，这有点hacky(允许我们从两个不同的对象读取和写入同一文件吗?)

I need to run a program with some flags set, check on its progress and report back to a server. So I need my script to avoid blocking while the program executes, but I also need to be able to read the output. Unfortunately, I don't think any of the methods available from Popen will read the output without blocking. I tried the following, which is a bit hack-y (are we allowed to read and write to the same file from two different objects?)

import time
import subprocess
from subprocess import *
with open("stdout.txt", "wb") as outf:
    with open("stderr.txt", "wb") as errf:
        command = ['Path\\To\\Program.exe', 'para', 'met', 'ers']
        p = subprocess.Popen(command, stdout=outf, stderr=errf)
        isdone = False
        while not isdone :
            with open("stdout.txt", "rb") as readoutf: #this feels wrong
                for line in readoutf:
                    print(line)
            print("waiting...\\r\\n")
            if(p.poll() != None) :
                done = True
            time.sleep(1)
        output = p.communicate()[0]    
        print(output)

不幸的是，直到命令终止后，Popen才似乎不会写入我的文件.

Unfortunately, Popen doesn't seem to write to my file until after the command terminates.

有人知道这样做的方法吗?我不是专用于使用python，但是我确实需要使用相同的脚本将POST请求发送到服务器，因此python似乎比shell脚本更容易选择.

Does anyone know of a way to do this? I'm not dedicated to using python, but I do need to send POST requests to a server in the same script, so python seemed like an easier choice than, say, shell scripting.

谢谢！ 会

推荐答案

基本上，您有3个选择:

Basically you have 3 options:

1. 使用threading读入另一个线程而不会阻塞主线程.
在标准输出上使用
2. select 代替stderr communicate.这样，您可以在数据可用时立即读取数据，并避免阻塞.
3. 让图书馆解决这个问题， twisted是显而易见的选择.

1. Use threading to read in another thread without blocking the main thread.
2. select on stdout, stderr instead of communicate. This way you can read just when data is available and avoid blocking.
3. Let a library solve this, twisted is a obvious choice.

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