AssertionError: can only start a process object created by current process

Question

目前我在主进程下创建了3个进程A、B、C。但是，我想在进程A中启动B和C，可以吗？

process.py

from multiprocessing import Process

procs = {}
import time

def test():
    print(procs)
    procs['B'].start()
    procs['C'].start()
    time.sleep(8)

    procs['B'].terminate()
    procs['C'].termiante()

    procs['B'].join()
    procs['C'].join()




def B():
    while True:
        print('+'*10)
        time.sleep(1)
def C():
    while True:
        print('-'*10)
        time.sleep(1)


procs['A'] = Process(target = test)
procs['B'] = Process(target = B)
procs['C'] = Process(target = C)

main.py

from process import *
print(procs)
procs['A'].start()
procs['A'].join()

我得到了错误 AssertionError: 只能启动当前进程创建的进程对象

是否有其他方法可以在 A 中启动进程 B 和 C？或者让A发送信号要求master进程启动B和C

Answer 1

我建议使用 Event 对象进行同步。它们允许跨流程触发某些操作。例如

from multiprocessing import Process, Event
import time

procs = {}


def test():
    print(procs)

    # Will let the main process know that it needs
    # to start the subprocesses
    procs['B'][1].set()
    procs['C'][1].set()
    time.sleep(3)

    # This will trigger the shutdown of the subprocess
    # This is cleaner than using terminate as it allows
    # you to clean up the processes if needed.
    procs['B'][1].set()
    procs['C'][1].set()


def B():
    # Event will be set once again when this process
    # needs to finish
    event = procs["B"][1]
    event.clear()
    while not event.is_set():
        print('+' * 10)
        time.sleep(1)


def C():
    # Event will be set once again when this process
    # needs to finish
    event = procs["C"][1]
    event.clear()
    while not event.is_set():
        print('-' * 10)
        time.sleep(1)


if __name__ == '__main__':
    procs['A'] = (Process(target=test), None)
    procs['B'] = (Process(target=B), Event())
    procs['C'] = (Process(target=C), Event())
    procs['A'][0].start()

    # Wait for events to be set before starting the subprocess
    procs['B'][1].wait()
    procs['B'][0].start()
    procs['C'][1].wait()
    procs['C'][0].start()

    # Join all the subprocess in the process that created them.
    procs['A'][0].join()
    procs['B'][0].join()
    procs['C'][0].join()

请注意，这段代码并不是很干净。在这种情况下只需要一个事件。但你应该明白主要思想。

此外，进程 A 不再需要，您可以考虑使用回调。如果您想链接一些异步操作，请参阅 concurrent.futures 模块。

AssertionError: can only start a process object created by current process

AssertionError: can only start a process object created by current process

python

multiprocessing

python-3.x

python-multiprocessing