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46 lines
1.8 KiB
46 lines
1.8 KiB
#coding=utf-8
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import threading
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import random
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import time
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class SemaphoreThread(threading.Thread):
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"""classusing semaphore"""
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availableTables=['A','B','C','D','E']
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def __init__(self,threadName,semaphore):
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"""initialize thread"""
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threading.Thread.__init__(self,name=threadName)
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self.sleepTime=random.randrange(1,6)
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#set the semaphore as a data attribute of the class
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self.threadSemaphore=semaphore
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def run(self):
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"""Print message and release semaphore"""
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#acquire the semaphore
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self.threadSemaphore.acquire()
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#remove a table from the list
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table=SemaphoreThread.availableTables.pop()
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print "%s entered;seated at table %s." %(self.getName(),table),
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print SemaphoreThread.availableTables
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time.sleep(self.sleepTime)
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#free a table
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print " %s exiting;freeing table %s." %(self.getName(),table),
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SemaphoreThread.availableTables.append(table)
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print SemaphoreThread.availableTables
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#release the semaphore after execution finishes
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self.threadSemaphore.release()
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threads=[] #list of threads
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#semaphore allows five threads to enter critical section
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threadSemaphore=threading.Semaphore(len(SemaphoreThread.availableTables))
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#创建一个threading.Semaphore对象，他最多允许5个线程访问临界区。
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#Semaphore类的一个对象用计数器跟踪获取和释放信号机的线程数量。
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#create ten threads
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for i in range(1,11):
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threads.append(SemaphoreThread("thread"+str(i),threadSemaphore))
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#创建一个列表，该列表由SemaphoreThread对象构成，start方法开始列表中的每个线程
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#start each thread
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for thread in threads:
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thread.start()
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