用 Popen 模仿 glib.spawn_async…

Question

函数 glib.spawn_async 允许您挂接三个回调，这些回调在 stdout、stderr 和进程完成时调用。

如何使用线程或 asyncio 模仿 subprocess 的相同功能？

我对功能比 threading/asynio 更感兴趣，但同时包含这两个功能的答案将获得赏金。

这是一个演示我想做什么的玩具程序：

import glib
import logging
import os
import gtk


class MySpawn(object):
    def __init__(self):
        self._logger = logging.getLogger(self.__class__.__name__)

    def execute(self, cmd, on_done, on_stdout, on_stderr):
        self.pid, self.idin, self.idout, self.iderr = \
            glib.spawn_async(cmd,
                             flags=glib.SPAWN_DO_NOT_REAP_CHILD,
                             standard_output=True,
                             standard_error=True)
        fout = os.fdopen(self.idout, "r")
        ferr = os.fdopen(self.iderr, "r")
        glib.child_watch_add(self.pid, on_done)
        glib.io_add_watch(fout, glib.IO_IN, on_stdout)
        glib.io_add_watch(ferr, glib.IO_IN, on_stderr)
        return self.pid


if __name__ == '__main__':
    logging.basicConfig(format='%(thread)d %(levelname)s:  %(message)s',
                        level=logging.DEBUG)
    cmd = '/usr/bin/git ls-remote https://github.com/DiffSK/configobj'.split()

    def on_done(pid, retval, *args):
        logging.info("That's all folks!…")

    def on_stdout(fobj, cond):
        """This blocks which is fine for this toy example…"""
        for line in fobj.readlines():
            logging.info(line.strip())
        return True

    def on_stderr(fobj, cond):
        """This blocks which is fine for this toy example…"""
        for line in fobj.readlines():
            logging.error(line.strip())
        return True

    runner = MySpawn()
    runner.execute(cmd, on_done, on_stdout, on_stderr)
    try:
        gtk.main()
    except KeyboardInterrupt:
        print('')

我应该补充一点，因为 readlines() 是阻塞的，上面将缓冲所有输出并立即发送。如果这不是你想要的，那么你必须使用 readline() 并确保在命令结束时你读完了之前没有读过的所有行。

Answer 1

asyncio有subprocess_exec，完全不用subprocess模块：

import asyncio

class Handler(asyncio.SubprocessProtocol):
    def pipe_data_received(self, fd, data):
        # fd == 1 for stdout, and 2 for stderr
        print("Data from /bin/ls on fd %d: %s" % (fd, data.decode()))

    def pipe_connection_lost(self, fd, exc):
        print("Connection lost to /bin/ls")

    def process_exited(self):
        print("/bin/ls is finished.")

loop = asyncio.get_event_loop()
coro = loop.subprocess_exec(Handler, "/bin/ls", "/")

loop.run_until_complete(coro)
loop.close()

有了子进程和线程，也很简单。您可以只为每个管道生成一个线程，并为进程生成一个线程 wait()：

import subprocess
import threading

class PopenWrapper(object):
    def __init__(self, args):
       self.process = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.DEVNULL)

       self.stdout_reader_thread = threading.Thread(target=self._reader, args=(self.process.stdout,))
       self.stderr_reader_thread = threading.Thread(target=self._reader, args=(self.process.stderr,))
       self.exit_watcher = threading.Thread(target=self._exit_watcher)

       self.stdout_reader_thread.start()
       self.stderr_reader_thread.start()
       self.exit_watcher.start()

    def _reader(self, fileobj):
        for line in fileobj:
            self.on_data(fileobj, line)

    def _exit_watcher(self):
        self.process.wait()
        self.stdout_reader_thread.join()
        self.stderr_reader_thread.join()
        self.on_exit()

    def on_data(self, fd, data):
        return NotImplementedError

    def on_exit(self):
        return NotImplementedError

    def join(self):
        self.process.wait()

class LsWrapper(PopenWrapper):
    def on_data(self, fd, data):
        print("Received on fd %r: %s" % (fd, data))

    def on_exit(self):
        print("Process exited.")


LsWrapper(["/bin/ls", "/"]).join()

但是，请注意 glib 不会使用线程异步执行回调。它使用事件循环，就像 asyncio 一样。这个想法是，在您的程序的核心是一个循环，该循环等待直到某些事情发生，然后同步执行关联的回调。在您的例子中，是 "data becomes available for reading on one of the pipes" 和 "the subprocess has exited"。通常，它还有 "the X11-server reported mouse movement"、"there's incoming network traffic" 等内容。您可以通过编写自己的事件循环来模拟 glib 的行为。在两个管道上使用 select module。如果 select 报告管道可读，但 read returns 没有数据，则进程可能已退出 - 在这种情况下调用子进程对象上的 poll() 方法来检查是否它已完成，如果有则调用您的退出回调，否则调用错误回调。

用 Popen 模仿 glib.spawn_async…

Mimicing glib.spawn_async with Popen…

python

multithreading

gtk

glib

python-asyncio