Python并发编程-线程同步(线程安全)

　　　　　　Python并发编程-线程同步(线程安全)

　　　　　　　　　　　　　　　　　　　　　　　作者：尹正杰

版权声明：原创作品，谢绝转载！否则将追究法律责任。

 

　　线程同步，线程间协调，通过某种技术，让一个线程访问某些数据时，其它线程不能访问这些数据，直到该线程完成对数据的操作。

 

一.Event

1>.Event的常用方法

Event事件，是线程通信机制中最简单的实现，使用一个内部的标记flag，通过flage的True或False的变化来进行操作。

常用方法如下:
    set():
　　　　标记为True。

    clear():
　　　　标记设置为Flase。

    is_set():
　　　　查询标记是否为True。

    wait(timeout=None):
　　　　设置等待标记为True的时长，None为无线等待。等到返回True，未等到超时了返回False。

2>.Event使用案例

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 
 7 from threading import Event,Thread
 8 import logging
 9  
10 FORMAT = "%(asctime)s %(threadName)s %(thread)s %(message)s"
11 logging.basicConfig(format=FORMAT,level=logging.INFO)
12 
13 def boss(event:Event):
14     logging.info("I'm boss,waiting for U")
15     event.wait()        #阻塞等待,直到event被标记为Ture
16     logging.info("Good Job.")
17 
18 def worker(event:Event,count=10):
19     logging.info("I'm working for U.")
20     cups = []
21     while not event.wait(0.5):      #使用wait等待0.5秒(相当于"time.sleep(0.5)"),若规定事件内event依旧标记依旧没有设置为True，则返回False
22         logging.info("make 1 cup")
23         cups.append(1)
24         if len(cups) >= count:
25             event.set()             #将标记设置为True
26             break
27     logging.info("I finished my job.cups={}".format(cups))
28 
29 event = Event()
30 print(event.is_set())               #event实例的标记默认为False
31 
32 b = Thread(target=boss,name="boss",args=(event,))
33 w = Thread(target=worker,name="worker",args=(event,))
34 b.start()
35 w.start()
2019-11-23 14:54:53,177 boss 10916 I'm boss,waiting for U
2019-11-23 14:54:53,178 worker 15672 I'm working for U.
False
2019-11-23 14:54:53,678 worker 15672 make 1 cup
2019-11-23 14:54:54,179 worker 15672 make 1 cup
2019-11-23 14:54:54,680 worker 15672 make 1 cup
2019-11-23 14:54:55,180 worker 15672 make 1 cup
2019-11-23 14:54:55,680 worker 15672 make 1 cup
2019-11-23 14:54:56,181 worker 15672 make 1 cup
2019-11-23 14:54:56,681 worker 15672 make 1 cup
2019-11-23 14:54:57,181 worker 15672 make 1 cup
2019-11-23 14:54:57,681 worker 15672 make 1 cup
2019-11-23 14:54:58,182 worker 15672 make 1 cup
2019-11-23 14:54:58,182 worker 15672 I finished my job.cups=[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
2019-11-23 14:54:58,182 boss 10916 Good Job.
以上代码执行结果戳这里

3>.定时器Timer(延迟执行)

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import threading
 7 import logging
 8 import time
 9 
10 FORMAT = "%(asctime)s %(threadName)s %(thread)s %(message)s"
11 logging.basicConfig(level=logging.INFO,format=FORMAT)
12 
13 def worker():
14     logging.info("working")
15     time.sleep(2)
16 
17 """
18     Timer是线程Thread的子类，Timer实例内部提供了一个finished属性，该属性是Event对象。
19     Timer是线程Thread的子类,就是线程类，具有线程的能力和特征。
20     它的实例时能够延时执行目标函数的线程，在真正执行目标函数之前，都可以cancel它。
21     cacel方法本质使用Event类实现。这并不是说，线程提供了取消的方法。
22 """
23 t = threading.Timer(4,worker)             #当t对象调用start方法后，等待4秒后执行worker函数
24 t.setName("timer")
25 
26 t.start()
27 # t.cancel()                               #本质上是在worker函数执行前对finished属性set方法操作，从而跳过了worker函数执行，达到了取消的效果。
28 
29 for _ in range(10):
30     print(threading.enumerate())
31     time.sleep(1)
[<_MainThread(MainThread, started 5332)>, <Timer(timer, started 6656)>]
[<_MainThread(MainThread, started 5332)>, <Timer(timer, started 6656)>]
[<_MainThread(MainThread, started 5332)>, <Timer(timer, started 6656)>]
[<_MainThread(MainThread, started 5332)>, <Timer(timer, started 6656)>]
[<_MainThread(MainThread, started 5332)>, <Timer(timer, started 6656)>]
2019-11-23 15:07:40,987 timer 6656 working
[<_MainThread(MainThread, started 5332)>, <Timer(timer, started 6656)>]
[<_MainThread(MainThread, started 5332)>]
[<_MainThread(MainThread, started 5332)>]
[<_MainThread(MainThread, started 5332)>]
[<_MainThread(MainThread, started 5332)>]
以上代码执行结果戳这里

  

二.Lock

1>.Lock的常用方法

锁，一旦线程获得锁，其它试图获取锁的线程将被阻塞。

锁:凡是存在资源共享争抢的地方都可以使用锁,从而只有一个使用者可以完全使用这个资源。

锁常用的方法如下:
    acquire(blocking=True,timeout=-1):
　　　　默认阻塞，阻塞可以设置超时事件。非阻塞时，timeout禁止设置。
　　　　成功获取锁，返回True，否则返回False

    release():
　　　　释放锁。可以从任何线程调用释放。
　　　　已上锁的锁，会被重置为unlocked
　　　　若在未上锁的锁上调用，则会抛出RuntimeError异常。

2>.Lock锁使用案例

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 from threading import Thread,Lock
 7 import logging
 8 import time
 9 
10 FORMAT = "%(asctime)s %(threadName)s %(thread)s %(message)s"
11 logging.basicConfig(level=logging.INFO,format=FORMAT)
12 
13 cpus = []
14 lock = Lock()
15 
16 def worker(count=10):
17     logging.info("I'm working for U.")
18     flag = False
19     while True:
20         lock.acquire()          #获取锁
21         if len(cpus) >= count:
22             flag = True
23         time.sleep(0.0001)      #为了看出线程切换效果
24         if not flag:
25             cpus.append(1)
26         lock.release()
27         if flag:
28             break
29     logging.info("I finished . cups = {}".format(len(cpus)))
30 
31 
32 for _ in range(10):
33     Thread(target=worker,args=(1000,)).start()
2019-11-23 16:03:35,225 Thread-1 16204 I'm working for U.
2019-11-23 16:03:35,226 Thread-2 14436 I'm working for U.
2019-11-23 16:03:35,226 Thread-3 1164 I'm working for U.
2019-11-23 16:03:35,226 Thread-4 10460 I'm working for U.
2019-11-23 16:03:35,227 Thread-5 5072 I'm working for U.
2019-11-23 16:03:35,227 Thread-6 12016 I'm working for U.
2019-11-23 16:03:35,227 Thread-7 9732 I'm working for U.
2019-11-23 16:03:35,228 Thread-8 15644 I'm working for U.
2019-11-23 16:03:35,228 Thread-9 104 I'm working for U.
2019-11-23 16:03:35,228 Thread-10 16508 I'm working for U.
2019-11-23 16:03:37,130 Thread-1 16204 I finished . cups = 1000
2019-11-23 16:03:37,132 Thread-3 1164 I finished . cups = 1000
2019-11-23 16:03:37,134 Thread-4 10460 I finished . cups = 1000
2019-11-23 16:03:37,136 Thread-2 14436 I finished . cups = 1000
2019-11-23 16:03:37,138 Thread-5 5072 I finished . cups = 1000
2019-11-23 16:03:37,140 Thread-6 12016 I finished . cups = 1000
2019-11-23 16:03:37,142 Thread-7 9732 I finished . cups = 1000
2019-11-23 16:03:37,144 Thread-8 15644 I finished . cups = 1000
2019-11-23 16:03:37,146 Thread-9 104 I finished . cups = 1000
2019-11-23 16:03:37,148 Thread-10 16508 I finished . cups = 1000
以上代码执行结果戳这里

3>.加锁和解锁(计数器类案例)

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import threading
 7 from threading import Thread,Lock
 8 import logging
 9 import time
10 
11 FORMAT = "%(asctime)s %(threadName)s %(thread)s %(message)s"
12 logging.basicConfig(level=logging.INFO,format=FORMAT)
13 
14 class Counter:
15     def __init__(self):
16         self._val = 0
17         self.__lock = Lock()
18 
19     @property
20     def value(self):
21         with self.__lock:
22             return self._val
23 
24     def inc(self):
25         try:
26             self.__lock.acquire()
27             self._val += 1
28         finally:
29             self.__lock.release()
30 
31     def dec(self):
32         with self.__lock:
33             self._val -= 1
34 
35 
36 def worker(c:Counter,count=100):
37     for _ in  range(count):
38         for i in range(-50,50):
39             if i < 0:
40                 c.dec()
41             else:
42                 c.inc()
43 
44 c = Counter()
45 c1 = 10
46 c2 = 10000
47 
48 for i in  range(c1):
49     Thread(target=worker,args=(c,c2)).start()
50 
51 
52 while True:
53     time.sleep(1)
54     print(threading.enumerate())
55     if threading.active_count() == 1:
56         print((c.value))
57         break
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-6, started 8300)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-2, started 10732)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-4, started 2624)>, <Thread(Thread-5, started 1620)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>, <Thread(Thread-1, started 17728)>, <Thread(Thread-3, started 2680)>, <Thread(Thread-7, started 7532)>, <Thread(Thread-8, started 9480)>, <Thread(Thread-9, started 11044)>, <Thread(Thread-10, started 7164)>]
[<_MainThread(MainThread, started 14856)>]
0
以上代码执行结果戳这里

4>.锁的应用场景

锁适用于访问和修改同一个共享资源的时候，即读写同一个资源的时候。

如果全部都是读取同一个共享资源需要锁吗?
　　不需要。因为这时可以认为共享资源是不可变的，每一次读取它都是一样的值，所以不用加锁

使用锁的注意事项:
  少用锁，必要时用锁。使用了锁，多线程访问被锁的资源时，就成了串行，要么排队执行，要么争抢执行
     举例，高速公路上车并行跑，可是到了省界只开放了一个收费口，过了这个口，车辆依然可以在多车道上一起跑。过收费口的时候，如果排队一辆辆过，加不加锁一样效率相当，但是一旦出现争抢，就必须加锁一辆辆过。注意，不管加不加锁，只要是一辆辆过，效率就下降了。
  加锁时间越短越好，不需要就立即释放锁
  一定要避免死锁

不使用锁，有了效率，但是结果是错的。

使用了锁，效率低下，但是结果是对的。

所以，我们是为了效率要错误结果呢?还是为了对的结果，让计算机去计算吧。

5>.非阻塞锁使用

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import threading
 7 import logging
 8 import time
 9 
10 FORMAT = "%(asctime)s %(threadName)s %(thread)-10d %(message)s"
11 logging.basicConfig(level=logging.INFO,format=FORMAT)
12 
13 lock = threading.Lock()
14 
15 def worker(l:threading.Lock):
16     while True:
17         flag = l.acquire(False)
18         if flag:
19             logging.info("do something.")       #为了显示效果，没有释放锁
20         else:
21             logging.info("try again")
22             time.sleep(1)
23 
24 for i in range(5):
25     threading.Thread(target=worker,name="worker={}".format(i),args=(lock,)).start()
2019-11-24 15:58:31,932 worker=0 123145354420224 do something.
2019-11-24 15:58:31,933 worker=0 123145354420224 try again
2019-11-24 15:58:31,933 worker=1 123145359675392 try again
2019-11-24 15:58:31,933 worker=2 123145364930560 try again
2019-11-24 15:58:31,934 worker=3 123145370185728 try again
2019-11-24 15:58:31,934 worker=4 123145375440896 try again
2019-11-24 15:58:32,933 worker=0 123145354420224 try again
2019-11-24 15:58:32,933 worker=1 123145359675392 try again
2019-11-24 15:58:32,934 worker=2 123145364930560 try again
2019-11-24 15:58:32,936 worker=4 123145375440896 try again
2019-11-24 15:58:32,936 worker=3 123145370185728 try again
2019-11-24 15:58:33,935 worker=0 123145354420224 try again
2019-11-24 15:58:33,935 worker=1 123145359675392 try again
2019-11-24 15:58:33,935 worker=2 123145364930560 try again
2019-11-24 15:58:33,940 worker=4 123145375440896 try again
2019-11-24 15:58:33,940 worker=3 123145370185728 try again
2019-11-24 15:58:34,939 worker=0 123145354420224 try again
2019-11-24 15:58:34,940 worker=1 123145359675392 try again
2019-11-24 15:58:34,940 worker=2 123145364930560 try again
2019-11-24 15:58:34,944 worker=4 123145375440896 try again
2019-11-24 15:58:34,945 worker=3 123145370185728 try again
2019-11-24 15:58:35,943 worker=1 123145359675392 try again
2019-11-24 15:58:35,944 worker=0 123145354420224 try again
2019-11-24 15:58:35,944 worker=2 123145364930560 try again
2019-11-24 15:58:35,948 worker=4 123145375440896 try again
2019-11-24 15:58:35,949 worker=3 123145370185728 try again
......
以上代码执行结果戳这里

 

三.可重入锁RLock 

1>.可重入锁不可跨越线程

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import threading
 7 import time
 8 
 9 lock = threading.RLock()
10 print(lock.acquire())                   #仅对当前线程上锁，但是代码并不会阻塞而是可以继续执行
11 print(lock.acquire(blocking=True))
12 print(lock.acquire(timeout=3))          #默认"blocking=True",因此可以设置值阻塞的超时时间，但当blocking=False时,timeout无法使用。
13 print(lock.acquire(blocking=False))
14 
15 print("main thread {}".format(threading.main_thread().ident))
16 print("lock in main thread {}".format(lock))
17 
18 print("{0} 我是分割线 {0}".format("*" * 15))
19 
20 lock.release()
21 lock.release()
22 lock.release()
23 lock.release()
24 # lock.release()                        #由于上面锁定的lock调用了4此锁定，因此解锁也只能是4次,若解锁次数超过上锁次数则抛出"RuntimeError: cannot release un-acquired lock"异常。
25 
26 print("main thread {}".format(threading.main_thread().ident))
27 print("lock in main thread {}".format(lock))
28 
29 print("{0} 我是分割线 {0}".format("*" * 15))
30 
31 print(lock.acquire(blocking=False))
32 print(lock.acquire(blocking=False))
33 print("main thread {}".format(threading.main_thread().ident))
34 print("lock in main thread {}".format(lock))
35 
36 # threading.Thread(target=lambda l:l.release(),args=(lock,)).start()          #可重入锁不可跨越线程，否则会抛出"RuntimeError: cannot release un-acquired lock"异常。
37 lock.release()                                                            #可重入锁无论是上锁还是解锁要求在同一个线程中。
38 
39 time.sleep(3)
40 print("main thread {}".format(threading.main_thread().ident))
41 print("lock in main thread {}".format(lock))
True
True
True
True
main thread 18096
lock in main thread <locked _thread.RLock object owner=18096 count=4 at 0x00000172263B7C60>
*************** 我是分割线 ***************
main thread 18096
lock in main thread <unlocked _thread.RLock object owner=0 count=0 at 0x00000172263B7C60>
*************** 我是分割线 ***************
True
True
main thread 18096
lock in main thread <locked _thread.RLock object owner=18096 count=2 at 0x00000172263B7C60>
main thread 18096
lock in main thread <locked _thread.RLock object owner=18096 count=1 at 0x00000172263B7C60>
以上代码执行结果戳这里

2>.为另一个线程传入同一个RLock对象

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import threading
 7 import time
 8 
 9 lock = threading.RLock()
10 
11 def sub(l:threading.RLock):
12     print("{}:{}".format(threading.current_thread(),l.acquire()))           #阻塞
13     print("{}:{}".format(threading.current_thread(),l.acquire()))
14     print("lock in sub thread {}".format(lock))
15     l.release()
16     print("release in sub 1")
17     print("lock in sub thread {}".format(lock))
18     l.release()
19     print("release in sub 2")
20     print("lock in sub thread {}".format(lock))
21 
22 
23 print(lock.acquire())
24 print("main thread {}".format(threading.main_thread().ident))
25 print("lock in main thread {}".format(lock))
26 
27 print("{0} 我是分割线 {0}".format("*" * 15))
28 
29 threading.Timer(2,sub,(lock,)).start()          #为另一个线程传入同一个lock对象
30 
31 print("in main thread, {}".format(lock.acquire()))
32 lock.release()
33 time.sleep(5)
34 print("release lock in main thread  =======",end="\n\n")
35 lock.release()
36 print("lock in main thread {}".format(lock))
True
main thread 2456
lock in main thread <locked _thread.RLock object owner=2456 count=1 at 0x000001BF29077B10>
*************** 我是分割线 ***************
in main thread, True
release lock in main thread  =======

lock in main thread <unlocked _thread.RLock object owner=0 count=0 at 0x000001BF29077B10>
<Timer(Thread-1, started 9072)>:True
<Timer(Thread-1, started 9072)>:True
lock in sub thread <locked _thread.RLock object owner=9072 count=2 at 0x000001BF29077B10>
release in sub 1
lock in sub thread <locked _thread.RLock object owner=9072 count=1 at 0x000001BF29077B10>
release in sub 2
lock in sub thread <unlocked _thread.RLock object owner=0 count=0 at 0x000001BF29077B10>
以上代码执行结果戳这里

3>.可重入锁相关总结

　　可重入锁，是线程相关的锁。可在同一个线程中获取锁，并可以继续在同一线程不阻塞多次获取锁。

　　当锁未释放完，其它线程获取锁就会阻塞，直到当前持有锁的线程释放完锁。

　　锁都应该使用完后释放。可重入锁也是锁，应该acquire多少次，就release多少次。
　　

 

四.Condition

1>.Condition常用方法

Condition(lock=None):
　　可传入一个Lock或者RLock对象，默认是RLock。

acquire(*args):
　　获取锁。

wait(self,timeout=None):
　　等待或超时。

notify(n=1):
　　唤醒至多指定数目个数的等待的线程，没有等待的线程就没有任何操作。

notify_all():
　　唤醒所有等待的线程。

2>.生产者消费者模型

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import logging
 7 from threading import Event,Thread,Condition
 8 import time
 9 import random
10 
11 FORMAT = "%(asctime)s %(threadName)s %(thread)s %(message)s"
12 logging.basicConfig(format=FORMAT,level=logging.INFO)
13 
14 class Dispachter:
15     def __init__(self):
16         self.data = None
17         self.event = Event()                #event只是为了使用方便,与逻辑无关
18         self.cond =Condition()
19 
20     def produce(self,total):
21         for _ in range(total):
22             data = random.randint(1,100)
23             with self.cond:
24                 logging.info(data)
25                 self.data = data
26                 # self.cond.notify_all()
27                 self.cond.notify(2)
28             self.event.wait(1)
29 
30     def consume(self):
31         while not self.event.is_set():
32             with self.cond:
33                 self.cond.wait()
34                 data = self.data
35                 logging.info("recieved {}".format(data))
36                 self.data = None
37             self.event.wait(0.5)
38 
39 d = Dispachter()
40 p = Thread(target=d.produce,name="producer",args=(10,))
41 
42 #增加消费者
43 for i in  range(5):
44     c = Thread(target=d.consume,name="consumer")
45     c.start()
46 
47 p.start()
2019-11-25 22:24:45,076 producer 12228 64
2019-11-25 22:24:45,076 consumer 7612 recieved 64
2019-11-25 22:24:45,076 consumer 18400 recieved None
2019-11-25 22:24:46,077 producer 12228 41
2019-11-25 22:24:46,077 consumer 15008 recieved 41
2019-11-25 22:24:46,078 consumer 16440 recieved None
2019-11-25 22:24:47,077 producer 12228 98
2019-11-25 22:24:47,077 consumer 14832 recieved 98
2019-11-25 22:24:47,077 consumer 7612 recieved None
2019-11-25 22:24:48,077 producer 12228 39
2019-11-25 22:24:48,077 consumer 18400 recieved 39
2019-11-25 22:24:48,078 consumer 15008 recieved None
2019-11-25 22:24:49,078 producer 12228 79
2019-11-25 22:24:49,078 consumer 16440 recieved 79
2019-11-25 22:24:49,078 consumer 14832 recieved None
2019-11-25 22:24:50,079 producer 12228 39
2019-11-25 22:24:50,079 consumer 7612 recieved 39
2019-11-25 22:24:50,080 consumer 15008 recieved None
......
以上代码执行结果戳这里

3>.Condition总结

　　Condition用于生产者消费者模型中，解决生产者消费者速度匹配的问题。

　　采用了通知机制，非常有效率。

　　使用方式：
　　　　使用Condition，必须先acquire，用完了要release，因为内部使用了锁，默认使用RLock，最好的方式是使用with上下文。
　　　　消费者这wait，等待通知。
　　　　生产者生产好消息，对消费者发通知，可以使用notify或者notify_all方法。

 

五.semaphore

1>.semaphore常用方法 

　　和Lock很像，信号量对象内部维护一个倒计数器，每一次acquire都会减1，当acquire方法发现计数为0就阻塞请求的线程，直到其它线程对信号量release后，计数大于0，恢复阻塞的线程。换句话说，计数器永远不会低于0，因为acquire的时候，发现是0，都会被阻塞。

　　semaphore常用方法如下:
　　　　Semaphore(value=1):
　　　　　　构造方法。value小于0，抛ValueError异常
　　　　acquire(blocking=True, timeout=None):
　　　　　　获取信号量，计数器减1，获取成功返回True
　　　　release():
　　　　　　释放信号量，计数器加1

2>.基本使用案例(存在release方法超界限的问题) 

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 
 7 from threading import Thread, Semaphore
 8 import logging
 9 import time
10 
11 FORMAT = '%(asctime)s %(threadName)-12s %(thread)-8s %(message)s'
12 logging.basicConfig(format=FORMAT, level=logging.INFO)
13 
14 def worker(s:Semaphore):
15     logging.info("in worker thread")
16     logging.info(s.acquire())
17     logging.info('worker thread over')
18 
19 
20 # 定义信号量的个数为3
21 s = Semaphore(3)
22 print(s.__dict__)
23 
24 logging.info(s.acquire())       #获取一把锁之后，"_value"计数器就会减1。
25 
26 
27 print(s.acquire(),s._value)
28 
29 print(s.acquire(),s._value)
30 
31 Thread(target=worker, name="worker",args=(s,)).start()
32 time.sleep(2)
33 logging.info(s.acquire(False))
34 logging.info(s.acquire(timeout=3))
35 
36 # 释放一个
37 logging.info('release one')
38 s.release()
39 print(s.__dict__)           #释放锁后可以被"worker"线程获取
40 
41 s.release()
42 s.release()
43 s.release()
44 s.release()
45 s.release()                 #此处我们可以故意多释放几次锁
46 
47 print(s.__dict__)           #竟然内置计数器"_value"达到了6(也有可能是5，因为worker线程中需要获取一把锁)，这样实际上超出我们的最大值，需要解决这个问题。
2019-11-26 09:54:22,345 MainThread   140735817298880 True
2019-11-26 09:54:22,345 worker       123145401769984 in worker thread
{'_cond': <Condition(<unlocked _thread.lock object at 0x102929170>, 0)>, '_value': 3}
True 1
True 0
2019-11-26 09:54:24,346 MainThread   140735817298880 False
2019-11-26 09:54:27,349 MainThread   140735817298880 False
2019-11-26 09:54:27,349 MainThread   140735817298880 release one
{'_cond': <Condition(<unlocked _thread.lock object at 0x102929170>, 0)>, '_value': 1}
{'_cond': <Condition(<unlocked _thread.lock object at 0x102929170>, 0)>, '_value': 6}
2019-11-26 09:54:27,350 worker       123145401769984 True
2019-11-26 09:54:27,350 worker       123145401769984 worker thread over
以上代码执行结果戳这里

3>.BoundedSemaphore类(有边界的信号量，不允许使用release超出初始化范围，否则，抛出“ValueError: Semaphore released too many times”异常)

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 
 7 from threading import Thread, BoundedSemaphore
 8 import logging
 9 import time
10 
11 FORMAT = '%(asctime)s %(threadName)-12s %(thread)-8s %(message)s'
12 logging.basicConfig(format=FORMAT, level=logging.INFO)
13 
14 def worker(s:BoundedSemaphore):
15     logging.info("in worker thread")
16     logging.info(s.acquire())
17     logging.info('worker thread over')
18 
19 
20 # 定义有边界信号量的个数为3
21 s = BoundedSemaphore(3)
22 print(s.__dict__)
23 
24 logging.info(s.acquire())       #获取一把锁之后，"_value"计数器就会减1。
25 
26 
27 print(s.acquire(),s._value)
28 
29 print(s.acquire(),s._value)
30 
31 Thread(target=worker, name="worker",args=(s,)).start()
32 time.sleep(2)
33 logging.info(s.acquire(False))
34 logging.info(s.acquire(timeout=3))
35 
36 # 释放一个
37 logging.info('release one')
38 s.release()
39 print(s.__dict__)           #释放锁后可以被"worker"线程获取
40 
41 s.release()
42 s.release()
43 s.release()
44 s.release()
45 s.release()                 #此处我们可以故意多释放几次锁，一旦release超出初始值的范围就抛出异常！
46 
47 print(s.__dict__)          
{'_cond': <Condition(<unlocked _thread.lock object at 0x102029170>, 0)>, '_value': 3, '_initial_value': 3}
True 1
True 0
2019-11-26 10:09:17,632 MainThread   140735817298880 True
2019-11-26 10:09:17,635 worker       123145507561472 in worker thread
2019-11-26 10:09:19,638 MainThread   140735817298880 False
{'_cond': <Condition(<unlocked _thread.lock object at 0x102029170>, 0)>, '_value': 1, '_initial_value': 3}
2019-11-26 10:09:22,643 MainThread   140735817298880 False
2019-11-26 10:09:22,644 MainThread   140735817298880 release one
Traceback (most recent call last):
  File "/yinzhengjie/python/devops/python基础/09.线程/04.信号量.py", line 43, in <module>
2019-11-26 10:09:22,644 worker       123145507561472 True
2019-11-26 10:09:22,644 worker       123145507561472 worker thread over
    s.release()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 483, in release
    raise ValueError("Semaphore released too many times")
ValueError: Semaphore released too many times
以上代码执行结果戳这里

4>.应用举例(一个简单的连接池)

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import random
 7 import threading
 8 import logging
 9 import time
10 
11 FORMAT = '%(asctime)s %(threadName)s %(thread)-8d %(message)s'
12 logging.basicConfig(level=logging.INFO, format=FORMAT)
13 
14 class Conn:
15     def __init__(self, name):
16         self.name = name
17 
18 """
19 连接池
20     因为资源有限，且开启一个连接成本高，所以，使用连接池。
21 
22 一个简单的连接池
23     连接池应该有容量(总数)，有一个工厂方法可以获取连接，能够把不用的连接返回，供其他调用者使用。
24 
25 使用信号量解决资源有限的问题。 
26     如果池中有资源，请求者获取资源时信号量减1，拿走资源。当请求超过资源数，请求者只能等待。当使用者用完归还资源后信号量加1，等待线程就可以被唤醒拿走资源。 
27     注意:这个连接池的例子不能用到生成环境，只是为了说明信号量使用的例子，连接池还有很多未完成功能。
28 """
29 class Pool:
30     def __init__(self, count:int):
31         self.count = count
32         #池中提前放着连接备用
33         self.pool = [self._connect('conn-{}'.format(i)) for i in range(self.count)]
34         self.semaphore = threading.Semaphore(self.count)
35 
36     def _connect(self, conn_name):
37         # 创建连接的方法，返回一个连接对象
38         return Conn(conn_name)
39 
40     def get_conn(self):
41         #从池中拿走一个连接
42         logging.info('get~~~~~~~~~~~~~')
43         self.semaphore.acquire()
44         logging.info('-------------------------')
45         return self.pool.pop()
46 
47     def return_conn(self, conn: Conn):
48         # 向池中返回一个连接对象
49         logging.info('return~~~~~~~~~~~~~')
50         self.pool.append(conn)
51         self.semaphore.release()
52 
53 def worker(pool:Pool):
54     conn = pool.get_conn()
55     logging.info(conn)
56     # 模拟使用了一段时间
57     time.sleep(random.randint(1, 5))
58     pool.return_conn(conn)
59 
60 # 初始化连接池
61 pool = Pool(3)
62 
63 for i in range(6):
64     threading.Thread(target=worker, name='worker-{}'.format(i), args=(pool,)).start()
2019-11-26 11:27:58,148 worker-0 123145324670976 get~~~~~~~~~~~~~
2019-11-26 11:27:58,148 worker-0 123145324670976 -------------------------
2019-11-26 11:27:58,148 worker-0 123145324670976 <__main__.Conn object at 0x102db0438>
2019-11-26 11:27:58,149 worker-1 123145329926144 get~~~~~~~~~~~~~
2019-11-26 11:27:58,149 worker-1 123145329926144 -------------------------
2019-11-26 11:27:58,149 worker-1 123145329926144 <__main__.Conn object at 0x102db03c8>
2019-11-26 11:27:58,149 worker-2 123145335181312 get~~~~~~~~~~~~~
2019-11-26 11:27:58,149 worker-2 123145335181312 -------------------------
2019-11-26 11:27:58,150 worker-2 123145335181312 <__main__.Conn object at 0x102db0240>
2019-11-26 11:27:58,150 worker-3 123145340436480 get~~~~~~~~~~~~~
2019-11-26 11:27:58,150 worker-4 123145345691648 get~~~~~~~~~~~~~
2019-11-26 11:27:58,151 worker-5 123145350946816 get~~~~~~~~~~~~~
2019-11-26 11:28:02,153 worker-0 123145324670976 return~~~~~~~~~~~~~
2019-11-26 11:28:02,153 worker-3 123145340436480 -------------------------
2019-11-26 11:28:02,154 worker-3 123145340436480 <__main__.Conn object at 0x102db0438>
2019-11-26 11:28:02,154 worker-1 123145329926144 return~~~~~~~~~~~~~
2019-11-26 11:28:02,154 worker-4 123145345691648 -------------------------
2019-11-26 11:28:02,154 worker-4 123145345691648 <__main__.Conn object at 0x102db03c8>
2019-11-26 11:28:03,154 worker-2 123145335181312 return~~~~~~~~~~~~~
2019-11-26 11:28:03,155 worker-5 123145350946816 -------------------------
2019-11-26 11:28:03,155 worker-5 123145350946816 <__main__.Conn object at 0x102db0240>
2019-11-26 11:28:05,155 worker-4 123145345691648 return~~~~~~~~~~~~~
2019-11-26 11:28:07,154 worker-3 123145340436480 return~~~~~~~~~~~~~
2019-11-26 11:28:08,159 worker-5 123145350946816 return~~~~~~~~~~~~~
以上代码执行结果戳这里

5>.信号量和锁

信号量:
　　可以多个线程访问共享资源，但这个共享资源数量有限。 

锁:
　　可以看做特殊的信号量，即信号量计数器初值为1。只允许同一个时间一个线程独占资源。

  

六.Queue的线程安全

 1 #！/usr/bin/env python
 2 #_*_conding:utf-8_*_
 3 #@author :yinzhengjie
 4 #blog:http://www.cnblogs.com/yinzhengjie
 5 
 6 import queue
 7 
 8 
 9 """
10 标准库queue模块，提供FIFO的Queue、LIFO的队列、优先队列。
11 
12 Queue类是线程安全的，适用于多线程间安全的交换数据。内部使用了Lock和Condition。
13 
14 为什么讲魔术方法时，说实现容器的大小，不准确? 
15     1>.如果不加锁，是不可能获得准确的大小的，因为你刚读取到了一个大小，还没有取走数据，就有可能被其他线程改了。 
16     2>.Queue类的size虽然加了锁，但是，依然不能保证立即get、put就能成功，因为读取大小和get、put方法是分开的。
17 """
18 
19 q = queue.Queue(8)
20 
21 if q.qsize() == 7:
22     q.put("abc")    #上下两句可能被打断
23 
24 if q.qsize() == 1:
25     q.get()         #未必会成功

 

posted @ 2019-11-19 05:47  尹正杰  阅读(856)  评论(0)  编辑  收藏  举报