进程的进阶教程

1. 进程的两种方式

1. 开启进程的第一种方式：

    
    
    
    
    
  ```
  from multiprocessing import Process
  import time
  
  def task(name):
    print(f'{name} is running')
    time.sleep(1)
    print(f'{name} is gone')
  if __name__ =='__main__':
    p = Process(target = task,args = ('常鑫',))
    p.start()(向操作系统发送一个开启子进程的信号，然后执行下一行)
    操作系统接收到信号，会在内存中开辟一个子进程的空间，copy主进程中的所有资源加载到子进程空间中，然后调用CPU去执行
    开辟子进程开销很大
    print('===主')
    所以永远会先执行主进程的代码
  ```

2. 开辟进程的第二种方式

    
    
    
    
    
  ```
  <pre class="from">```
  from multiprocessing import Process
  import time
  class MyProcess(Process):
    def __init__(self,name):
        super().__init()
        self.name = name
  
    def run(self):
        print(f'{self.name} is running')
        time.sleep(1)
        print(f'{self.name} is gone')
  
  if __name__ =='__main__':
    p = MyProcess('zhangsan')
    p.start()
    print('===主')
  ```
  ```

3. 简单应用

2. 获取进程pid

1. os.getpid() 获取子进程的进程id（PID）
2. os.getppid()获取主进程的进程id（PID）

from multiprocessing import Process
import time
import os
def task(name):
 print(f'{os.getpid()}')
 time.sleep(2)
 print(f'{os.getppid()}')

if __name__ =="__main__":
 p = Process(target=task,args = ('长兴',))
 p.start()
 print(f'===主{os.getpid()}')
子进程中的主进程id是py文件的子进程id

3. 验证进程之间的空间隔离

1. 不可变得数据类型/可变的数据类型(都是空间隔离)

from multiprocessing import Process
import time
name = '太白'#li = ['丽丽']
def task():
 global name 
 name = '杆子'
 #li.append('刚子')
 print(f'子进程：{name/li}')

if __name__ == "__main__":
 p = Process(target = task)
 p.start()
 time.sleep(2)
 print(name/li)

4. join（***）让主进程等待子进程结束之后再执行主进程

1. 单个join（子进程结束之后执行主进程）

from multiprocessing import Process
import time
def task(name):
 print(f'{name} is running')
 time.sleep(2)
 print(f'{name} is gone')
if __name__ == '__main__':
 p = Process(target = task,args = ('长兴',))
 p.start()
 p.join()
 print('==主开始')

1. 多个子进程使用join

from multiprocessing import Process
import time
def task(name,sec):
 print(f'{name} is running')
 time.sleep(sec)
 print(f'{name} is gone')

if __name__ == '__main__':
 p1 = Process(target = task,args = ('长兴',1))
 p2 = Process(target = task,args = ('立业',2))
 p3 = Process(target = task,args = ('海狗',3))
 p1.start()
 p2.satrt()
 p3.start()
 #join 只针对主进程，如果join下面多次join，他是不阻塞的
 p1.join()
 p2.join()
 p3.join()
 print(f'==主{time.time() - start_time}')

from multiprocessing import Process
import time
def task(name,sec):
 print(f'{name} is running')
 time.sleep(sec)
 print(f'{name} is gone')

if __name__ == '__main__':
 p1 = Process(target = task,args = ('长兴',1))
 p2 = Process(target = task,args = ('立业',2))
 p3 = Process(target = task,args = ('海狗',3))
 p1.start()
 p2.satrt()
 p3.start()
 #join 只针对主进程，如果join下面多次join，他是不阻塞的
 p1.join()
 print(f'==主1：{time.time()-start_time()}')
 p2.join()
 print(f'==主2：{time.time()-start_time()}')
 p3.join()
 print(f'==主3:{time.time() - start_time}')

1. 优化上面的代码

from multiprocessing import Process
import time
def task(sec):
 print(f'is running')
 time.sleep(sec)
 print(f'is gone')

if __name__ =='__main__':
 p1 = Process(target = task,args = ('长兴',1))
 p2 = Process(target = task,args = ('立业',2))
 p3 = Process(target = task,args = ('海狗',3))
 p1.start()
 p2.satrt()
 p3.start()
 #join 只针对主进程，如果join下面多次join，他是不阻塞的
 p1.join()
 p2.join()
 p3.join()

 li =[]
 for i in range(1,4):
     p = Process(target = task,args = (i,))
     li.append(p)
     p.start()
 for i in li:
     i.join()
 print(f'==主：{time.time()-start_time}')
 join就是阻塞，主进程有join,主进程下面的代码一律不执行，直到进程执行完毕之后，再执行  

5. 进程的其他参数

terminate（）杀死子进程
is_alive()判断子进程是否存活

from multiprocessing import Process
import time
def task(name):
    print(f'{name} is running')
    time.sleep(2)
    print(f'{name} is gone')

if __name__ == '__main__':
    # p = Process(target=task,args=('长兴',))
    p = Process(target=task,args=('长兴',),name = 'alex')
    p.start()
    time.sleep(1)
    p.terminate()#杀死子进程
    p.join()
    time.sleep(0.5)
    print(p.is_alive())
    print(p.name)
    p.name = 'sb'
    print(p.name)
    print('==主开始')

6. 守护进程：子进程守护着主进程，只要主进程结束，子进程跟着就结束

from multiprocessing import Process
import time
def task(name):
    print(f'{name} is running')
    time.sleep(2)
    print(f'{name} is gone')
if __name__ == '__main__':
    p = Process(target=task,args = ('常鑫',))
    p.daemon = True#讲子进程设置为守护进程，只要主进程结束，守护进程马上就会结束
    一定要在子进程开始之前设置
    p.start()
    time.sleep(1)
    print('===主')