python3 进程和线程

进程和线程

1. 进程：内存独立，线程共享同一进程的内存
2. 进程是资源的集合，线程是执行单位
3. 进程之间不能直接互相访问，同一进程中的程可以互相通信
4. 创建新进程消耗系统资源，线程非常轻量，只保存线程运行时的必要数据，如上下文、程序堆栈信息
5. 同一进程里的线程可以相互控制，父进程可以控制子进程

 1 import threading
 2 import time
 3
 4 def sayhi(num):
 5     print(‘num:‘,num)
 6     time.sleep(3)
 7
 8 a = threading.Thread(target=sayhi,args=(1,))
 9 b = threading.Thread(target=sayhi,args=(2,))
10 now1 = time.time()
11 print(now1)
12 a.start()
13 b.start()
14 now2 = time.time()
15 print(now2)
16 print(threading.active_count())
17 # 包含主线程，总共3个
18 print(a.getName())
19 print(b.getName())
20
21 class MyThread(threading.Thread):
22     def __init__(self,n):
23         threading.Thread.__init__(self)
24         self.n = n
25
26         def run(self):
27             print(‘running on thread $s‘%self.n)
28             time.sleep(3)
29 now3 = time.time()
30 print(now3)
31 t1 = MyThread(1)
32 t2 = MyThread(2)
33 t1.start()
34 t2.start()
35 print(t1.getName())
36 print(t2.getName())
37 now4 = time.time()
38 print(now4)
39
40 thread_list = []
41 for i in range(10):
42     s1 = threading.Thread(target=sayhi,args=(i,))
43     s1.start()
44     thread_list.append(s1)
45 now5 = time.time()
46 print(now5)
47 for r in thread_list:
48     r.join() # s1.wait()
49 print(‘--work done--‘)
50 now6 = time.time()
51 print(now6)
52 print(‘primary‘.center(20,‘-‘))
53
54
55 for ii in range(10):
56     s2 = threading.Thread(target=sayhi)
57     s2.setDaemon(s2)
58     s2.start()