python - multiprocessing : Process のサブクラス化と Queue による通信

• サブクラス化する事で状態変数を保持できる
• Queue を使うことで安全に情報のやり取りができる

from multiprocessing import Process, Queue

class Counter(Process):
    label = ' @'
    def __init__(self, start, queue):
        self.state = start
        self.post = queue
        Process.__init__(self)
    def run(self):
        for i in range(3):
            time.sleep(1)
            self.state += 1
            print(self.label, self.pid, self.state)
            self.post.put([self.pid, self.state])
            print(self.label, self.pid, '-')
           
if __name__ == '__main__':
    print('start',os.getpid())
    expected = 9
    post = Queue()
    p = Counter(0, post)
    q = Counter(100, post)
    r = Counter(1000, post)
    p.start()
    q.start()
    r.start()
    while expected:
        time.sleep(0.5)
        try:
            data = post.get(block=False)
        except :
            print 'no data...'
        else:
            print('posted:', data)
            expected -= 1
    p.join()
    q.join()
    r.join()
    print('finish', os.getpid(), r.exitcode)