python—day30

Added: Daemon

Daemon example:

from multiprocessing import  Process

import time

def foo():
    print(123)
    time.sleep(1)
    print('end123')

def bar():
    print(456)
    time.sleep(3)
    print('end456')

if __name__ == '__main__':
    p1 = Process(target=foo)
    p2 = Process(target=bar)
    p2.daemon = True
    p1.start()

    p2.start()

    print('====>')

Daemon application:

 1 import time
 2 import random
 3 from multiprocessing import Process,JoinableQueue
 4 
 5 def consumer(name,q):
 6     while True:
 7         res = q.get()
 8         time.sleep(random.randint(1,3))
 9         print('%s 吃了%s' %(name,res))
10         q.task_done()
11 
12 def producer(name,q,food):
13     for i in range(5):
14         time.sleep(random.randint(1,3))
15         res = '%s%s' %(i,food)
16         q.put(res)
17         print('%s生产了%s' %(name,res))
18 
19 if __name__ == '__main__':
20     q = JoinableQueue()
21 
22     p1 = Process(target=producer,args=('kermit1',q,'bianbian1'))
23     p2 = Process(target=producer,args=('kermit2',q,'bianbian2'))
24     p3 = Process(target=producer,args=('kermit3',q,'bianbian3'))
25 
26     c1 = Process(target=consumer,args=('田秩玮1',q))
27     c2 = Process(target=consumer,args=('田秩玮2',q))
28 
29     c1.daemon = True
30     c2.daemon = True
31 
32     p1.start()
33      p2.start()
 34      p3.start()
 35      c1.start()
 36      c2.start()
 37  
38  
39      p1.join()
 40      p2.join()
 41      p3.join()
 42  
43      q.join( ) #Once it ends, it means that the consumer has finished fetching things 
44  
45      print ( ' The main process ends ' )

Thread:

1. What is a thread?

　　Thread refers to the working process of a pipeline;

　　A process is not an execution unit at all, a process is actually a resource unit;

　　A process has its own thread, and the thread is the execution unit;

2. Thread VS Process

　　1. Threads in the same thread share resources in the process, and thread resources in different processes must be isolated;

　　2. The overhead of creating threads is much smaller than that of processes;

There are two ways to start a thread:

method one:

 1 from threading import Thread
 2 import  time
 3 def task(name):
 4     print('%s' %name)
 5     time.sleep(1)
 6 
 7 if __name__ == '__main__':
 8     t = Thread(target=task,args=('kermit',))
 9     t.start()
10     print('===主线程')

Method 2: It is recommended to use your own inherited Thread, self.name will bring its own name

1 class MyThread(Thread):
2     def run(self):
3         print('%s is running...' %self.name)
4         time.sleep(1)
5 
6 if __name__ == '__main__':
7     t = MyThread()
8     t.start()
9     print('主线程...')

Daemon thread:

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