如何在 Python 进程池中创建子进程？

from multiprocessing import Pool, Process, forkserverimport timedef print_run(msg):    print('msg.%s' % msg)    time.sleep(2)def print_log(msg):    p = Process(target=print_run,                args=(msg,))    p.start()    p.join()    print('msg is : %s' % msg)    time.sleep(1)def set_multprocess():    # 使用 forkserver 来允许子进程创建子进程    forkserver.start(set_forkserver_parallelism)    pool = Pool(processes=10)    for i in range(20):        pool.apply_async(func=print_log, args=(str(i),))    pool.close()    pool.join()    print('finished')# 设置 forkserver 的并行度def set_forkserver_parallelism(n):    """Set the parallelism to be n * number of processes."""    n = max(n, 1)    forkserver.set_forkserver_ parallelism(n)if __name__ == '__main__':    set_multprocess()