我有最初提问者的问题，但不希望调用线程。我将Jesse的解决方案与来自管道的直接read()和我自己的行读取缓冲处理程序混合在一起(然而，我的子进程- ping -总是写入<系统页面大小的整行)。我通过读入一个gobject-registered io watch来避免忙碌的等待。这些天我通常在gobject MainLoop中运行代码以避免线程。

def set_up_ping(ip, w):
    # run the sub-process
    # watch the resultant pipe
    p = subprocess.Popen(['/bin/ping', ip], stdout=subprocess.PIPE)
    # make stdout a non-blocking file
    fl = fcntl.fcntl(p.stdout, fcntl.F_GETFL)
    fcntl.fcntl(p.stdout, fcntl.F_SETFL, fl | os.O_NONBLOCK)
    stdout_gid = gobject.io_add_watch(p.stdout, gobject.IO_IN, w)
    return stdout_gid # for shutting down

观察者是

def watch(f, *other):
    print 'reading',f.read()
    return True

主程序建立一个ping，然后调用gobject邮件循环。

def main():
    set_up_ping('192.168.1.8', watch)
    # discard gid as unused here
    gobject.MainLoop().run()

任何其他工作都附加到gobject中的回调。

现有的解决方案不适合我(详情见下文)。最后成功的是使用read(1)实现readline(基于这个答案)。后者不阻塞:

from subprocess import Popen, PIPE
from threading import Thread
def process_output(myprocess): #output-consuming thread
    nextline = None
    buf = ''
    while True:
        #--- extract line using read(1)
        out = myprocess.stdout.read(1)
        if out == '' and myprocess.poll() != None: break
        if out != '':
            buf += out
            if out == '\n':
                nextline = buf
                buf = ''
        if not nextline: continue
        line = nextline
        nextline = None

        #--- do whatever you want with line here
        print 'Line is:', line
    myprocess.stdout.close()

myprocess = Popen('myprogram.exe', stdout=PIPE) #output-producing process
p1 = Thread(target=process_output, args=(myprocess,)) #output-consuming thread
p1.daemon = True
p1.start()

#--- do whatever here and then kill process and thread if needed
if myprocess.poll() == None: #kill process; will automatically stop thread
    myprocess.kill()
    myprocess.wait()
if p1 and p1.is_alive(): #wait for thread to finish
    p1.join()

为什么现有的解决方案不起作用:

Solutions that require readline (including the Queue based ones) always block. It is difficult (impossible?) to kill the thread that executes readline. It only gets killed when the process that created it finishes, but not when the output-producing process is killed. Mixing low-level fcntl with high-level readline calls may not work properly as anonnn has pointed out. Using select.poll() is neat, but doesn't work on Windows according to python docs. Using third-party libraries seems overkill for this task and adds additional dependencies.

一种解决方案是让另一个进程执行对该进程的读取，或者创建一个带有超时的进程线程。

这是一个超时函数的线程版本:

http://code.activestate.com/recipes/473878/

但是，是否需要在stdout传入时读取它? 另一种解决方案可能是将输出转储到一个文件中，然后使用p.t wait()等待进程完成。

f = open('myprogram_output.txt','w')
p = subprocess.Popen('myprogram.exe', stdout=f)
p.wait()
f.close()


str = open('myprogram_output.txt','r').read()

I also faced the problem described by Jesse and solved it by using "select" as Bradley, Andy and others did but in a blocking mode to avoid a busy loop. It uses a dummy Pipe as a fake stdin. The select blocks and wait for either stdin or the pipe to be ready. When a key is pressed stdin unblocks the select and the key value can be retrieved with read(1). When a different thread writes to the pipe then the pipe unblocks the select and it can be taken as an indication that the need for stdin is over. Here is some reference code:

import sys
import os
from select import select

# -------------------------------------------------------------------------    
# Set the pipe (fake stdin) to simulate a final key stroke
# which will unblock the select statement
readEnd, writeEnd = os.pipe()
readFile = os.fdopen(readEnd)
writeFile = os.fdopen(writeEnd, "w")

# -------------------------------------------------------------------------
def getKey():

    # Wait for stdin or pipe (fake stdin) to be ready
    dr,dw,de = select([sys.__stdin__, readFile], [], [])

    # If stdin is the one ready then read it and return value
    if sys.__stdin__ in dr:
        return sys.__stdin__.read(1)   # For Windows use ----> getch() from module msvcrt

    # Must finish
    else:
        return None

# -------------------------------------------------------------------------
def breakStdinRead():
    writeFile.write(' ')
    writeFile.flush()

# -------------------------------------------------------------------------
# MAIN CODE

# Get key stroke
key = getKey()

# Keyboard input
if key:
    # ... do your stuff with the key value

# Faked keystroke
else:
    # ... use of stdin finished

# -------------------------------------------------------------------------
# OTHER THREAD CODE

breakStdinRead()

选择模块帮助您确定下一个有用的输入在哪里。

但是，您几乎总是更喜欢使用单独的线程。一个是阻塞读取stdin，另一个是阻塞你不想阻塞的地方。

我的问题有点不同，因为我想从正在运行的进程中收集stdout和stderr，但最终是一样的，因为我想在小部件生成时在小部件中呈现输出。

我不希望使用队列或额外的线程来解决许多建议的解决方案，因为执行运行另一个脚本并收集其输出这样的常见任务应该不需要它们。

在阅读了建议的解决方案和python文档后，我解决了以下实现的问题。是的，它只适用于POSIX，因为我正在使用select函数调用。

我同意，对于这样一个常见的脚本任务，文档是令人困惑的，实现是尴尬的。我相信旧版本的python对Popen有不同的默认值和不同的解释，所以造成了很多困惑。这似乎对Python 2.7.12和3.5.2都很有效。

关键是将bufsize=1设置为行缓冲，然后universal_newlines=True处理为文本文件而不是二进制文件，这似乎成为设置bufsize=1时的默认值。

class workerThread(QThread):
   def __init__(self, cmd):
      QThread.__init__(self)
      self.cmd = cmd
      self.result = None           ## return code
      self.error = None            ## flag indicates an error
      self.errorstr = ""           ## info message about the error

   def __del__(self):
      self.wait()
      DEBUG("Thread removed")

   def run(self):
      cmd_list = self.cmd.split(" ")   
      try:
         cmd = subprocess.Popen(cmd_list, bufsize=1, stdin=None
                                        , universal_newlines=True
                                        , stderr=subprocess.PIPE
                                        , stdout=subprocess.PIPE)
      except OSError:
         self.error = 1
         self.errorstr = "Failed to execute " + self.cmd
         ERROR(self.errorstr)
      finally:
         VERBOSE("task started...")
      import select
      while True:
         try:
            r,w,x = select.select([cmd.stdout, cmd.stderr],[],[])
            if cmd.stderr in r:
               line = cmd.stderr.readline()
               if line != "":
                  line = line.strip()
                  self.emit(SIGNAL("update_error(QString)"), line)
            if cmd.stdout in r:
               line = cmd.stdout.readline()
               if line == "":
                  break
               line = line.strip()
               self.emit(SIGNAL("update_output(QString)"), line)
         except IOError:
            pass
      cmd.wait()
      self.result = cmd.returncode
      if self.result < 0:
         self.error = 1
         self.errorstr = "Task terminated by signal " + str(self.result)
         ERROR(self.errorstr)
         return
      if self.result:
         self.error = 1
         self.errorstr = "exit code " + str(self.result)
         ERROR(self.errorstr)
         return
      return

ERROR, DEBUG和VERBOSE仅仅是将输出打印到终端的宏。

这个解决方案在我看来是99.99%有效的，因为它仍然使用了阻塞readline函数，所以我们假设子进程很好，输出完整的行。

我欢迎反馈，以改进解决方案，因为我仍然是Python新手。