1 队列读写
# -*- coding: utf-8 -*-
"""
多进程 共享 队列 multiprocessing.Process
逻辑:
一个进程往队列写数据,一个进程从读写读数据
写进程完了后,主进程强行结束读进程
使用:
1. 创建队列 q = multiprocessing.Queue() ,默认无限大小,可以指定大小
2. 把队列 q 当参数传给 子进程 执行代码, 猜测应该不能通过全局变量的方式访问
3. 在子进程中读写队列数据 q.put(<data>) q.get()
参考:
方法
'cancel_join_thread', 'close', 'empty', 'full', 'get', 'get_nowait', 'join_thread', 'put', 'put_nowait', 'qsize'
"""
from multiprocessing import Queue, Process
import time
def write(q):
for i in ['a','b','c','d']:
time.sleep(2)
q.put(i)
print ('put {0} to queue'.format(i))
def read(q):
while 1:
time.sleep(2)
result = q.get()
print ("get {0} from queue".format(result))
def main():
q = Queue()
pw = Process(target=write, args=(q,))
pr = Process(target=read, args=(q,))
pw.start()
pr.start()
pw.join()
pr.terminate() # 强行终止读进程
if __name__ == '__main__':
main()
"""
Out:
put a to queue
get a from queue
put b to queue
get b from queue
put c to queue
get c from queue
put d to queue
get d from queue
"""
2 队列实现生产者、消费者
# -*- coding: utf-8 -*-
"""
多进程 生产者 消费者模型,使用队列实现 multiprocessing.Queue
逻辑:
1个生产者,1个消费者在2个不同的进程中操作同一个队列
生产者的速度是消费者的3倍
"""
import multiprocessing
import random
import time
# 生产者
class producer(multiprocessing.Process):
def __init__(self, queue):
multiprocessing.Process.__init__(self) # 父类构造
self.queue = queue
def run(self):
for i in range(10):
item = random.randint(0, 256)
# 往队列写数据
self.queue.put(item)
print("Process Producer: item %d appended to queue %s "
%(item, self.name))
time.sleep(1)
print("The size of queue is %s"
% self.queue.qsize())
# 消费者
class consumer(multiprocessing.Process):
def __init__(self, queue):
multiprocessing.Process.__init__(self) # 父类构造
self.queue = queue
def run(self):
while True:
if (self.queue.empty()):
print("the queue is empty")
break
else:
time.sleep(2)
# 从队列读取数据,队列为空会阻塞,这做了非空判断,只有一个进程读,不会阻塞
item = self.queue.get()
print("Process Consumer: item %d poped from by %s "
% (item, self.name))
time.sleep(1)
if __name__ == '__main__':
# 多进程共享对列
queue = multiprocessing.Queue()
## 启动生产者、消费者
process_producer = producer(queue)
process_consumer = consumer(queue)
process_producer.start()
process_consumer.start()
process_producer.join()
process_consumer.join()
"""
Out:
the queue is empty
Process Producer: item 225 appended to queue producer-1
The size of queue is 1
Process Producer: item 101 appended to queue producer-1
The size of queue is 2
Process Producer: item 50 appended to queue producer-1
The size of queue is 3
Process Producer: item 217 appended to queue producer-1
The size of queue is 4
Process Producer: item 75 appended to queue producer-1
The size of queue is 5
Process Producer: item 45 appended to queue producer-1
The size of queue is 6
Process Producer: item 19 appended to queue producer-1
The size of queue is 7
Process Producer: item 157 appended to queue producer-1
The size of queue is 8
Process Producer: item 127 appended to queue producer-1
The size of queue is 9
Process Producer: item 223 appended to queue producer-1
The size of queue is 10
"""