Python: Multithreading between Java subproccess and Python listener?

It's pretty hard to tell here, but I think what you're asking is how to:

• Launch a program in the background.
• Send it input, as if it came from a user on the console.
• Read its output that it tries to display to a user on the console.
• At the same time, run another thread that does other stuff.

The last one is pretty easy; in fact, you've mostly written it, you just need to add a thread1.start() somewhere.

The subprocess module lets you launch a program and control its input and output. It's easiest if you want to just feed in all the input at once, wait until it's done, then process all the output, but obviously that's not your case here, so it's a bit more involved:

minecraft = subprocess.Popen(['java', 'path/to/minecraft_server.jar', '-other', 'args],
                             stdin=subprocess.PIPE, 
                             stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

stdout과 stderr을 하나로 병합하고 있습니다. 개별적으로 읽거나 stderr을 / dev / null로 보내려면 문서를 참조하십시오. 모두 매우 간단합니다. 여기서 가정하는 동안 minecraft_server모든 명령, 모든 응답 및 모든 정보 메시지가 정확히 한 줄 (즉, a로 끝나는 1K 미만의 텍스트 \n) 인 간단한 줄 기반 프로토콜 을 사용 한다고 가정합니다. .

이제 입력을 보내려면 다음과 같이하십시오.

minecraft.stdin.write('Make me a sandwich\n')

또는 Python 3.x에서 :

minecraft.stdin.write(b'Make me a sandwich\n')

출력을 읽으려면 다음을 수행하십시오.

response = minecraft.stdout.readline()

That works just like a regular file. But note that it works like a binary file. In Python 2.x, the only difference is that newlines don't get automatically converted, but in Python 3.x, it means you can only write bytes (and compatible objects), not strs, and you will receive bytes back. There are good reasons for that, but if you want to get pipes that act like text files instead, see the universal_newlines (and possibly bufsize) arguments under Frequently Used Arguments and Popen Constructor.

Also, it works like a blocking file. With a regular file, this rarely matters, but with a pipe, it's quite possible that there will be data later, but there isn't data yet (because the server hasn't written it yet). So, if there is no output yet (or not a complete line's worth, since I used readline()), your thread just blocks, waiting until there is.

If you don't want that, you probably want to create another thread to service stdout. And its function can actually look pretty similar to what you've got:

def listener():
    for line in minecraft.stdout:
        if line.strip() == "Server can't keep up!":
            minecraft.stdin.write("Restart Universe\n")

Now that thread can block all day and there's no problem, because your other threads are still going.

Well, not quite no problem.

First it's going to be hard to cleanly shut down your program.

More seriously, the pipes between processes have a fixed size; if you don't service stdout fast enough, or the child doesn't service stdin fast enough, the pipe can block. And, the way I've written things, if the stdin pipe blocks, we'll be blocked forever in that stdin.write and won't get to the next read off stdout, so that can block too, and suddenly we're both waiting on each other forever.

You can solve this by having another thread to service stdout. The subprocess module itself includes an example, in the Popen._communicate function used by all the higher-level functions. (Make sure to look at Python 3.3 or later, because earlier versions had bugs.)

Python 3.4 이상 (또는 PyPI에서 백 포트가없는 3.3)을 사용하는 경우 대신를 사용 asyncio하여 이벤트 루프를 중심으로 프로그램을 다시 작성하고 리액터 기반 네트워크 서버를 작성하는 것과 동일한 방식으로 입력 및 출력을 처리 할 수 ​​있습니다. 그게 2017 년에 멋진 아이들이하는 일이지만 2014 년 말에 많은 사람들은 여전히 ​​새롭고 무섭다고 생각했습니다.

이 모든 것이 귀하가 서명 한 것보다 훨씬 더 많은 작업처럼 들린다면 pexpect, 지루한 세부 사항을 많이 정리하고 귀하의 경우에 사실 일 수있는 몇 가지 단순화 된 가정을 만드는를 사용하는 것이 좋습니다.