python 多进程读写文件

import time
from multiprocessing import Process, JoinableQueue, cpu_count
import csv


####处理一条数据的方法
def deal_line(line, writer, csv_file):
    writer.writerow((line[3], line[1]))
    csv_file.flush()#重点,在多进程中写文件需要尽快刷新,否则可能会导致数据丢失

####消费者模型
def consumer(queue, writer, csv_file):
    while True:
        line = queue.get()
        deal_line(line, writer, csv_file)
        queue.task_done()
####生产者模型
def producer(queue):
    with open('test.txt', 'r') as f:
        for line in f:
            queue.put(line)

####启动N个生产者N个消费者模型
def main():
    with open('t1.csv', 'w+') as csv_file:
        writer = csv.writer(csv_file)
        queue = JoinableQueue(8)#可限制队列长度
        pc = Process(target=producer, args=(queue,))
        pc.start()

        #多消费者
        for _ in range(cpu_count()):
            c1 = Process(target=consumer, args=(queue, writer, csv_file))
            c1.daemon = True
            c1.start()
        pc.join()#等待生产者进程全部生成完毕
        queue.join()# 等待所有数据全部处理完毕

        # 当某些些进程是死循环时可强制终止
        # pc.terminate()

if __name__ == '__main__':

    now = lambda: time.time()
    start = now()
    main()
    print("Time:", now() - start)