主进程的多处理回调 - Python

Question

有没有办法使用多处理从创建的进程回调主进程？ 假设我有 main.py，它使用如下所示的多重处理创建三个进程

from multiprocessing import Process
from child import createNewProcess

def callbackFunction(data):
   print(data)

if __name__ == "__main__"
   process = []
   for i in range(3):
        p = Process(target=createNewProcess, args=(callback,))
        process.append(p)
   [x.start() for x in process]

，而 child.py 看起来像

def createNewProcess(externalCB):
    # do something and call external callback
    data = 10 + 12
    externalCB(data)

我想调用callbackFunction()，它在创建的进程的主进程上下文中可用。 但在上面的情况下，它在自己的进程中创建了三个新的callbackFunction() 对象，并调用自己上下文中的对象。

如何使用多处理进程调用主callbackFunction()上下文？

Answer 1

代码片段，其中包含使用队列传递适当的回调并将数据传回主进程上的线程的示例：

from multiprocessing import Process, Queue, current_process
from threading import Thread
from time import sleep

def foo_process(data, cb_queue, cb):
    print(f"data from process [{current_process().pid}]: {data}")
    sleep(.1) # time to flush stdout so print statement is usually in correct order
              # (may still be out of order on IPython)
    cb_queue.put((cb, data))

def foo_thread(data):
    print(f"data from cb_thread in process [{current_process().pid}]: {data*2}")

def callback_caller(cb_queue):
    for func, *args in iter(cb_queue.get, None): #pass None to exit thread
        func(*args)

if __name__ == "__main__":
    print(f"main pid: [{current_process().pid}]")
    q = Queue()

    p = Process(target=foo_process, args=(3.15, q, foo_thread))
    p.start()
    
    #It's advisable (if possible) to always create processes first then threads.
    #this primarily applies to using "fork", but it's good to know / good habit.
    t = Thread(target=callback_caller, args=(q,))
    t.start()

    p.join()

    q.put(None) #send shutdown signal to callback_caller
    t.join()