使用Python的交互式输入/输出 [英] Interactive input/output using Python

问题描述

我有一个与用户交互的程序(行为类似于shell)，并且我想使用Python子进程模块以交互方式运行它. 这意味着，我希望可以写入标准输入并立即从标准输出中获取输出.我尝试了这里提供的许多解决方案，但是似乎没有一个可以满足我的需求.

I have a program that interacts with the user (acts like a shell), and I want to run it using the Python subprocess module interactively. That means, I want the possibility to write to standard input and immediately get the output from standard output. I tried many solutions offered here, but none of them seems to work for my needs.

我编写的代码基于 运行交互式在Python中执行命令 .

The code I've written is based on Running an interactive command from within Python.

import Queue
import threading
import subprocess
def enqueue_output(out, queue):
    for line in iter(out.readline, b''):
        queue.put(line)
    out.close()

def getOutput(outQueue):
    outStr = ''
    try:
        while True: # Adds output from the queue until it is empty
            outStr += outQueue.get_nowait()

    except Queue.Empty:
        return outStr

p = subprocess.Popen("./a.out", stdin=subprocess.PIPE, stout=subprocess.PIPE, stderr=subprocess.PIPE, bufsize = 1)
#p = subprocess.Popen("./a.out", stdin=subprocess.PIPE, stout=subprocess.PIPE, stderr=subprocess.PIPE, shell=False, universal_newlines=True)

outQueue = Queue()
errQueue = Queue()

outThread = Thread(target=enqueue_output, args=(p.stdout, outQueue))
errThread = Thread(target=enqueue_output, args=(p.stderr, errQueue))

outThread.daemon = True
errThread.daemon = True

outThread.start()
errThread.start()

p.stdin.write("1\n")
p.stdin.flush()
errors = getOutput(errQueue)
output = getOutput(outQueue)

p.stdin.write("5\n")
p.stdin.flush()
erros = getOutput(errQueue)
output = getOutput(outQueue)

问题是队列保持为空，就像没有输出一样. 仅当我将标准程序需要执行和终止的所有输入都写到标准输入中时，我才得到输出(这不是我想要的).例如，如果我做类似的事情:

The problem is that the queue remains empty, as if there is no output. Only if I write to standard input all the input that the program needs to execute and terminate, then I get the output (which is not what I want). For example, if I do something like:

p.stdin.write("1\n5\n")
errors = getOutput(errQueue)
output = getOutput(outQueue)

有没有办法做我想做的事?

Is there a way to do what I want to do?

该脚本将在Linux机器上运行.我更改了脚本，并删除了Universal_newlines = True +将bufsize设置为1，并在写入后立即刷新了标准输入.仍然没有任何输出.

The script will run on a Linux machine. I changed my script and deleted the universal_newlines=True + set the bufsize to 1 and flushed standard input immediately after write. Still I don't get any output.

第二次尝试:

我尝试了此解决方案，它对我有用:

I tried this solution and it works for me:

from subprocess import Popen, PIPE

fw = open("tmpout", "wb")
fr = open("tmpout", "r")
p = Popen("./a.out", stdin = PIPE, stdout = fw, stderr = fw, bufsize = 1)
p.stdin.write("1\n")
out = fr.read()
p.stdin.write("5\n")
out = fr.read()
fw.close()
fr.close()

推荐答案

在Linux上针对此问题的两种解决方案:

Two solutions for this issue on Linux:

第一个是使用文件将输出写入其中，并同时读取输出:

First one is to use a file to write the output to, and read from it simultaneously:

from subprocess import Popen, PIPE

fw = open("tmpout", "wb")
fr = open("tmpout", "r")
p = Popen("./a.out", stdin = PIPE, stdout = fw, stderr = fw, bufsize = 1)
p.stdin.write("1\n")
out = fr.read()
p.stdin.write("5\n")
out = fr.read()
fw.close()
fr.close()

第二，正如塞巴斯蒂安(J.F. Sebastian)提出的那样，是使用fnctl模块使p.stdout和p.stderr管道不阻塞:

Second, as J.F. Sebastian offered, is to make p.stdout and p.stderr pipes non-blocking using fnctl module:

import os
import fcntl
from subprocess import Popen, PIPE  
def setNonBlocking(fd):
    """
    Set the file description of the given file descriptor to non-blocking.
    """
    flags = fcntl.fcntl(fd, fcntl.F_GETFL)
    flags = flags | os.O_NONBLOCK
    fcntl.fcntl(fd, fcntl.F_SETFL, flags)

p = Popen("./a.out", stdin = PIPE, stdout = PIPE, stderr = PIPE, bufsize = 1)
setNonBlocking(p.stdout)
setNonBlocking(p.stderr)

p.stdin.write("1\n")
while True:
    try:
        out1 = p.stdout.read()
    except IOError:
        continue
    else:
        break
out1 = p.stdout.read()
p.stdin.write("5\n")
while True:
    try:
        out2 = p.stdout.read()
    except IOError:
        continue
    else:
        break

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