How to transfer the data after the completion of the second process to the first one?

Question

I have application X.exe and Y.exe. First, I start server X, after which I have to start Y 20 times and get 20 different PIDs. Due to certain circumstances, I have to run these processes at the same time, so I run X and the script issuing PIDs as processes. I don’t understand how to transfer the data generated by the second process to the first one in order to work with them already in it. Here is my code:

from subprocess import Popen, PIPE
from multiprocessing import Process


def firstproc():
    process = Popen(
        'X.exe',
        stdout=PIPE)
    while True:
        chunk = process.stdout.readline()
        print(chunk)

def secondproc():
    def getPID():
        return Popen('Y.exe').pid
    return [getPID() for _ in range(20)]

def main():
    p1 = Process(target=firstproc, args=())
    p2 = Process(target=secondproc, args=())
    p1.start()
    p2.start()
if __name__ == "__main__":
    main()

The first process runs indefinitely

Asked By: Alexander

||

Source

Answer 1

To write a process1 stdout line in any process2 stdin you can use this code:

from subprocess import Popen, PIPE
from threading import Thread, Lock

class Processes:
    def __init__(self):
        self.p1: Popen = None
        self.p2: Popen = None
        self.lock = Lock()
        self.lock2 = Lock()
        self.lock.acquire()
        self.lock2.acquire()
        self.p2_run = True

    def firstproc(self):
        self.p1 = Popen(
            'X.exe',
            stdout=PIPE)
        while self.p2_run:
            line = self.p1.stdout.readline()
            self.lock2.acquire()
            if self.p2_run:
                self.p2.communicate(line)
            self.lock.release()

    def secondproc(self):
        def getPID():
            self.p2 = Popen('Y.exe', stdin=PIPE)
            self.lock2.release()
            self.lock.acquire()
            return self.p2.pid
        pids = []
        for _ in range(8):
            pids.append(getPID())

        self.p2_run = False
        self.lock2.release()
        return pids

def main():
    t = Processes()
    p1 = Thread(target=t.firstproc, args=())
    p1.start()
    p2 = Thread(target=t.secondproc, args=())
    p2.start()
    p1.join()
if __name__ == "__main__":
    main()

I use threading to synchronize processes to write in stdin and to read stdout.

Answered By: MauriceLambert

How to transfer the data after the completion of the second process to the first one?

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