并发编程（五）GIL、死锁现象与递归锁、信号量、Event事件、线程queue

所有线程抢的是GIL锁&＃xff0c;或者说所有线程抢的是执行权限线程1抢到GIL锁&＃xff0c;拿到执行权限&＃xff0c;开始执行&＃xff0c;然后加了一把Lock&＃xff0c;还没有执行完毕&＃xff0c;即线程1还未释放Lock&＃xff0c;有可能线程2抢到GIL锁&＃xff0c;开始执行&＃xff0c;执行过程中发现Lock还没有被线程1释放&＃xff0c;于是线程2进入阻塞&＃xff0c;被夺走执行权限&＃xff0c;有可能线程1拿到GIL&＃xff0c;然后正常执行到释放Lock。。。这就导致了串行运行的效果既然是串行&＃xff0c;那我们执行t1.start()t1.joint2.start()t2.join()这也是串行执行啊&＃xff0c;为何还要加Lock呢&＃xff0c;需知join是等待t1所有的代码执行完&＃xff0c;相当于锁住了t1的所有代码&＃xff0c;而Lock只是锁住一部分操作共享数据的代码

from multiprocessing import Process
from threading import Thread
import os,time
def work():res&＃61;0for i in range(10000):res*&＃61;iif __name__ &＃61;&＃61; &＃39;__main__&＃39;:l&＃61;[]print(os.cpu_count())start&＃61;time.time()for i in range(4):p&＃61;Process(target&＃61;work)#p&＃61;Thread(target&＃61;work)
l.append(p)p.start()for p in l:p.join()stop&＃61;time.time()print(&＃39;run time is %s&＃39; %(stop-start))

from multiprocessing import Process
from threading import Thread
import threading
import os,time
def work():time.sleep(2)print(&＃39;&＃61;&＃61;&＃61;>&＃39;)if __name__ &＃61;&＃61; &＃39;__main__&＃39;:l&＃61;[]print(os.cpu_count())start&＃61;time.time()for i in range(400):# p&＃61;Process(target&＃61;work)p&＃61;Thread(target&＃61;work)l.append(p)p.start()for p in l:p.join()stop&＃61;time.time()print(&＃39;run time is %s&＃39; %(stop-start))

from threading import Thread,Lock,RLock
import timemutexA&＃61;Lock()
mutexB&＃61;Lock()class Mythead(Thread):def run(self):self.f1()self.f2()def f1(self):mutexA.acquire()print(&＃39;%s 抢到A锁&＃39; %self.name)mutexB.acquire()print(&＃39;%s 抢到B锁&＃39; %self.name)mutexB.release()mutexA.release()def f2(self):mutexB.acquire()print(&＃39;%s 抢到了B锁&＃39; %self.name)time.sleep(2)mutexA.acquire()print(&＃39;%s 抢到了A锁&＃39; %self.name)mutexA.release()mutexB.release()if __name__ &＃61;&＃61; &＃39;__main__&＃39;:for i in range(100):t&＃61;Mythead()t.start()

from threading import Thread,Semaphore
import time,random
sm&＃61;Semaphore(5) #允许5个线程并发运行&＃xff0c;但是5个线程可以不是原来那5个def task(name):sm.acquire()print(&＃39;%s 正在上厕所&＃39; %name)time.sleep(random.randint(1,3))sm.release()if __name__ &＃61;&＃61; &＃39;__main__&＃39;:for i in range(20):t&＃61;Thread(target&＃61;task,args&＃61;(&＃39;路人%s&＃39; %i,))t.start()

from threading import Thread,Event
import timeevent&＃61;Event()def light():print(&＃39;红灯正亮着&＃39;)time.sleep(3)event.set() #绿灯亮def car(name):print(&＃39;车%s正在等绿灯&＃39; %name)event.wait() #等灯绿print(&＃39;车%s通行&＃39; %name)if __name__ &＃61;&＃61; &＃39;__main__&＃39;:# 红绿灯t1&＃61;Thread(target&＃61;light)t1.start()# 车for i in range(10):t&＃61;Thread(target&＃61;car,args&＃61;(i,))t.start()

import queueq&＃61;queue.Queue()
q.put(&＃39;first&＃39;)
q.put(&＃39;second&＃39;)
q.put(&＃39;third&＃39;)print(q.get())
print(q.get())
print(q.get())&＃39;&＃39;&＃39;
结果(先进先出):
first
second
third
&＃39;&＃39;&＃39;

import queueq&＃61;queue.Queue()
q.put(&＃39;first&＃39;)
q.put(&＃39;second&＃39;)
q.put(&＃39;third&＃39;)print(q.get())
print(q.get())
print(q.get())&＃39;&＃39;&＃39;
结果(先进先出):
third
second
first
&＃39;&＃39;&＃39;

import queueq&＃61;queue.PriorityQueue()
#put进入一个元组,元组的第一个元素是优先级(通常是数字,也可以是非数字之间的比较),数字越小优先级越高
q.put((20,&＃39;a&＃39;))
q.put((10,&＃39;b&＃39;))
q.put((30,&＃39;c&＃39;))print(q.get())
print(q.get())
print(q.get())&＃39;&＃39;&＃39;
结果(数字越小优先级越高,优先级高的优先出队):
(10, &＃39;b&＃39;)
(20, &＃39;a&＃39;)
(30, &＃39;c&＃39;)
&＃39;&＃39;&＃39;