python 进程间通信

1. 不能使用python自带的queue进行通信，不然无法接受到数据

from queue import Queue

def producer(queue):
    queue.put("a")
    time.sleep(2)

def consumer(queue):
    time.sleep(2)
    data = queue.get()
    print(data)

if __name__ == "__main__":
    queue = Queue(10)
    my_producer = Process(target=producer, args=(queue,))
    my_consumer = Process(target=consumer, args=(queue,))
    my_producer.start()
    my_consumer.start()
    my_producer.join()
    my_consumer.join()

2. 必须使用multiprocessing中的Queue

import time
from multiprocessing import Process, Queue, Pool, Manager, Pipe

def producer(queue):
    queue.put("a")
    time.sleep(2)

def consumer(queue):
    time.sleep(2)
    data = queue.get()
    print(data)

if __name__ == "__main__":
    queue = Queue(10)
    my_producer = Process(target=producer, args=(queue,))
    my_consumer = Process(target=consumer, args=(queue,))
    my_producer.start()
    my_consumer.start()
    my_producer.join()
    my_consumer.join()

3. 全局变量不适用于多进程编程，可以使用与多线程编程

def producer(a):
    a += 100
    time.sleep(2)

def consumer(a):
    time.sleep(2)
    print(a)

if __name__ == "__main__":
    a = 1
    my_producer = Process(target=producer, args=(a,))
    my_consumer = Process(target=consumer, args=(a,))
    my_producer.start()
    my_consumer.start()
    my_producer.join()
    my_consumer.join()

4. multiprocessing中的queue不能用于pool进程池, pool中的进程间通信需要使用manager中的queue

def producer(queue):
    queue.put("a")
    time.sleep(2)

def consumer(queue):
    time.sleep(2)
    data = queue.get()
    print(data)

if __name__ == "__main__":
    queue = Manager().Queue(10)
    pool = Pool(2)

    pool.apply_async(producer, args=(queue,))
    pool.apply_async(consumer, args=(queue,))

    pool.close()
    pool.join()

5. 通过pipe实现进程间通信，pipe的性能高于queue，因为queque中加了锁

def producer(pipe):
    pipe.send("bobby")

def consumer(pipe):
    print(pipe.recv())

if __name__ == "__main__":
    recevie_pipe, send_pipe = Pipe()
    #pipe只能适用于两个进程
    my_producer= Process(target=producer, args=(send_pipe, ))
    my_consumer = Process(target=consumer, args=(recevie_pipe,))

    my_producer.start()
    my_consumer.start()
    my_producer.join()
    my_consumer.join()

6. 多线程可以想用共享变量，但是必须使用Manager中的dict

def add_data(p_dict, key, value):
    p_dict[key] = value

if __name__ == "__main__":
    progress_dict = Manager().dict()

    first_progress = Process(target=add_data, args=(progress_dict, "bobby1", 22))
    second_progress = Process(target=add_data, args=(progress_dict, "bobby2", 23))

    first_progress.start()
    second_progress.start()
    first_progress.join()
    second_progress.join()

    print(progress_dict)