Handling Concurrent Processes in Python Scripting

I aim to develop a script capable of concurrently running two processes, namely process1.exe and process2.exe. Following their initiation, the script will conduct essential checks and execute additional code segments. Moreover, within the application, if process2.exe terminates prematurely, it necessitates terminating process1.exe and exiting the ongoing script. Under such circumstances, all operations, including the check script executed after launching both processes, must cease. Conversely, upon completing the checks, the script should await the closure of process2.exe to subsequently close process1.exe.

The code that I am running is as follows:

import psutil
import subprocess
import multiprocessing
import os
import time

def findPID():
    process_pid = {}
    process_list = [p.info for p in psutil.process_iter(['name', 'pid'])]
    
    for proc in process_list:
        if proc['name'] == "process2.exe" or proc['name'] == "process1.exe":
            process_name = proc['name']
            process_pid[f"{process_name}"] = proc["pid"]

    return process_pid


def killSimunteneously(event, queue, running_process, process_pid):
    while True:
        if not psutil.pid_exists(process_pid['process2.exe']):
            try:
                process_to_kill = psutil.Process(process_pid['process1.exe'])
                process_to_kill.terminate()
                break
            except:
                break
            
        else:
            time.sleep(2)
    
    queue.put("killSimunteneously Completed!")
    event.set()

    if running_process.is_alive():
        print("Terminating checkStatus")
        running_process.terminate()

def checkStatus(event, queue):
    # Some Code

    queue.put("checkStatus Completed!")

    if not event.is_set():
        print("Waiting for killSimunteneously")
        event.wait()
    
def main():
    os.startfile(".\process2.exe")
    
    subprocess.Popen([".\process1.exe"], creationflags=subprocess.CREATE_NEW_CONSOLE)
    
    bg_process_PID = findPID()
    
    queue = multiprocessing.Queue()
    event = multiprocessing.Event()

    p1 = multiprocessing.Process(target=checkStatus, args=(event, queue))
    p1.start()

    p2 = multiprocessing.Process(target=killSimunteneously, args=(event, queue, p1, bg_process_PID,))
    p2.start()

    p1.join()
    p2.join()

    while not queue.empty():
        print(queue.get())

if __name__ == "__main__":
main()

The error when executing the script:

Traceback (most recent call last):
  File "D:\codes\script.py", line 71, in <module>
    main()
  File "D:\codes\script.py", line 62, in main
    p2.start()
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\process.py", line 121, in start
    self._popen = self._Popen(self)
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\context.py", line 336, in _Popen
    return Popen(process_obj)
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\popen_spawn_win32.py", line 93, in __init__
    reduction.dump(process_obj, to_child)
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle 'weakref.ReferenceType' object
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 116, in spawn_main
    exitcode = _main(fd, parent_sentinel)
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\multiprocessing\spawn.py", line 126, in _main
    self = reduction.pickle.load(from_parent)
EOFError: Ran out of input

Running checkStatus() and killSimultaneously() sequentially, without employing multiprocessing.Process(), functioned correctly. However, if process2.exe terminated before the checks concluded, it failed to terminate process1.exe.

Initially, I attempted this without utilizing a queue or event. The remainder of the code remained unchanged. However, in this scenario, process2.exe was initiated three times instead of once, which was an issue encountered when executing the .exe file generated by PyInstaller. The .py file, on the other hand, behaved as anticipated.

I removed part of your code. I hope I didn't misunderstand your needs.

import subprocess
import multiprocessing


def checkStatus(event, queue):
    # Some Code

    queue.put("checkStatus Completed!")

    if not event.is_set():
        print("Waiting for killSimunteneously")
        event.wait()


def main():
    process1 = subprocess.Popen(["./process1.exe"])
    process2 = subprocess.Popen(["./process2.exe"], creationflags=subprocess.CREATE_NEW_CONSOLE)

    queue = multiprocessing.Queue()
    event = multiprocessing.Event()

    p1 = multiprocessing.Process(target=checkStatus, args=(event, queue))
    p1.start()

    # Wait for process 2 to finish
    process2.wait()

    # Terminate process 1 after process 2 has finished.
    process1.terminate()
    event.set()

    p1.join()

    while not queue.empty():
        print(queue.get())


if __name__ == "__main__":
    main()