多线程 VS 多进程（三）
原创
线程替代方案
- subprocess
- 完全跳过线程，使用进程
- 是派生进程的主要替代方案
- python2.4后引入
- multiprocessiong
- 使用threading接口派生，使用子进程
- 允许为多核或者多cpu派生进程，接口跟threading非常相似
- python2.6后引入
- concurrent.futures - 新的异步执行模块 - 任务级别的操作 - python3.2后引入多进程
- 进程间通讯(InterprocessCommunication, IPC)
- 进程之间无任何共享状态
- 进程的创建
- 直接生成Process实例对象，案例19 ```python import multiprocessing from time import sleep, ctime
def clock(interval): while True: print("The time is %s" % ctime()) sleep(interval) if __name__ == '__main__': p = multiprocessing.Process(target=clock, args=(5, )) p.start() while True: print("sleeping......") sleep(1) ``` sleeping...... The time is Tue Aug 13 19:47:41 2019 sleeping...... sleeping...... sleeping...... sleeping...... sleeping...... The time is Tue Aug 13 19:47:46 2019 sleeping...... sleeping...... sleeping...... sleeping...... ...- 派生子类，案例20
```python
import multiprocessing
from time import sleep, ctime
class ClockProcess(multiprocessing.Process): ''' 两个函数比较重要 1. init构造函数
2. run
'''
def __init__(self, interval):
super(ClockProcess, self).__init__()
self.interval = interval
def run(self):
while True:
print("The time is %s" % ctime())
sleep(self.interval)
if __name__ == '__main__': p = ClockProcess(3) p.start() ``` The time is Tue Aug 13 19:48:49 2019 The time is Tue Aug 13 19:48:52 2019 The time is Tue Aug 13 19:48:55 2019 The time is Tue Aug 13 19:48:58 2019 The time is Tue Aug 13 19:49:01 2019 The time is Tue Aug 13 19:49:04 2019 ...- 在os中查看pid，ppid以及他们的关系
- 案例21 ```python from multiprocessing import Process import os
def info(title): print(title) print("module name:", __name__) # 得到父亲进程的id print("parent process:", os.getppid()) # 得到本身进程的id print("process id:", os.getpid()) def f(name): info('function f') print('hello', name) if __name__ == '__main__': info('main line') p = Process(target=f, args=('bob', )) p.start() p.join() ``` main line module name: __main__ parent process: 11900 process id: 18832 function f module name: __mp_main__ parent process: 18832 process id: 20868 hello bob- 生产者消费者模型
- JoinableQueue
- 案例22 ```python import multiprocessing from time import ctime
def consumer(input_q): print("Into consumer:", ctime) while True: # 处理项 item = input_q.get() print('pull', item, 'out of q') input_q.task_done() # 发出信号通知任务完成 print("Out of consumer:", ctime()) ## 此句未执行，因为q.join()收集到四个task_done()信号后，主进程启动，未等到print此句完成，程序就结束了 def producer(sequence, output_q): print("Into procuder:", ctime()) for item in sequence: output_q.put(item) print('put', item, 'into q') print('Out of procuder', ctime()) # 建立进程 if __name__ == '__main__': q = multiprocessing.JoinableQueue() # 进行消费者进程 cons_p = multiprocessing.Process(target=consumer, args=(q, )) cons_p.daemon = True cons_p.start() # 生产多个项，sequence代表要发送给消费者的项序列 # 在实践中，这可能是生成器的输出或通过一些其他地方生产出来 sequence = [1, 2, 3, 4] producer(sequence, q) # 等待所有项被处理 q.join() ``` Into procuder: Tue Aug 13 19:50:38 2019 put 1 into q put 2 into q put 3 into q put 4 into q Out of procuder Tue Aug 13 19:50:38 2019 Into consumer: <built-in function ctime> pull 1 out of q pull 2 out of q pull 3 out of q pull 4 out of q- 队列中哨兵的使用，案例23
```python
import multiprocessing
from time import ctime
# 设置哨兵问题 def consumer(input_q): print("Into consumer:", ctime()) while True: item = input_q.get() if item is None: break print("pull", item, "out of q") print ("Out of consumer:", ctime()) ## 此句执行完成，再转入主进程 def producer(sequence, output_q): print ("Into procuder:", ctime()) for item in sequence: output_q.put(item) print ("put", item, "into q") print ("Out of procuder:", ctime()) if __name__ == '__main__': q = multiprocessing.Queue() cons_p = multiprocessing.Process(target = consumer, args = (q,)) cons_p.start() sequence = [1,2,3,4] producer(sequence, q) q.put(None) cons_p.join() ``` Into procuder: Tue Aug 13 19:51:23 2019 put 1 into q put 2 into q put 3 into q put 4 into q Out of procuder: Tue Aug 13 19:51:23 2019 Into consumer: Tue Aug 13 19:51:24 2019 pull 1 out of q pull 2 out of q pull 3 out of q pull 4 out of q Out of consumer: Tue Aug 13 19:51:24 2019- 哨兵的改进，案例24
```python
import multiprocessing
from time import ctime
def consumer(input_q): print ("Into consumer:", ctime()) while True: item = input_q.get() if item is None: break print("pull", item, "out of q") print ("Out of consumer:", ctime()) def producer(sequence, output_q): for item in sequence: print ("Into procuder:", ctime()) output_q.put(item) print ("Out of procuder:", ctime()) if __name__ == '__main__': q = multiprocessing.Queue() cons_p1 = multiprocessing.Process (target = consumer, args = (q,)) cons_p1.start() cons_p2 = multiprocessing.Process (target = consumer, args = (q,)) cons_p2.start() sequence = [1,2,3,4] producer(sequence, q) q.put(None) q.put(None) cons_p1.join() cons_p2.join() ``` Into procuder: Tue Aug 13 19:52:08 2019 Out of procuder: Tue Aug 13 19:52:08 2019 Into procuder: Tue Aug 13 19:52:08 2019 Out of procuder: Tue Aug 13 19:52:08 2019 Into procuder: Tue Aug 13 19:52:08 2019 Out of procuder: Tue Aug 13 19:52:08 2019 Into procuder: Tue Aug 13 19:52:08 2019 Out of procuder: Tue Aug 13 19:52:08 2019 Into consumer: Tue Aug 13 19:52:08 2019 pull 1 out of q pull 2 out of q pull 3 out of q pull 4 out of q Out of consumer: Tue Aug 13 19:52:08 2019 Into consumer: Tue Aug 13 19:52:08 2019 Out of consumer: Tue Aug 13 19:52:08 2019原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。
如有侵权，请联系 cloudcommunity@tencent.com 删除。
原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。
如有侵权，请联系 cloudcommunity@tencent.com 删除。
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