Python: Thread Advanced

1, daemon thread

Import Time fromThreadingImportThreaddeffunc ():Print('start executing a child thread') Time.sleep (3)    Print('Child thread Execution complete') T= Thread (target=func) T.setdaemon (True)#The Process settings daemon is a property daemon = TrueT.start () T2= Thread (target=func) T2.start () T2.join ()#waiting for T2 to end

# The daemon daemon is waiting for the main process or the code in the main thread to finish executing
# t2 = Thread (Target=func)
# T2.start ()   ---> Code execution complete
# The daemon thread is over.
# The main thread is not over wait T2 continue execution
# t2 execution Complete main thread end

# t2 = Thread (Target=func)
# T2.start ()
# T2.join ()  # Wait for T2 to finish executing this line of code before execution is complete
# t2 Thread Execution Complete
# No code in main thread, end of daemon thread

2, lock

Import Time fromThreadingImportThread fromThreadingImportLockdeffunc ():GlobalN Time.sleep (2) lock.acquire () Temp= N#get n from the processTime.sleep (0.01) n= Temp-1#get results, then store back to processlock.release () n= 100Lock=Lock () t_lst= [] forIinchRange (100): T= Thread (target=func) T.start () t_lst.append (t) [T.join () forTinchT_lst]Print(n)#GIL is not lock data but lock thread#Special cases in multi-threading are still locked to the data

3, deadlock

Import Time fromThreadingImportRlock fromThreadingImportThreadm= KZ = Rlock ()#defEat (name): Kz.acquire ()#get the keys .    Print('%s got the chopsticks.'%name) M.acquire ()Print('%s got a face.'%name)Print('%s eating Noodles'%name) m.release () kz.release ()defEAT2 (name): M.acquire ()#no key .    Print('%s got a face.'%name) Time.sleep (1) Kz.acquire ()Print('%s got the chopsticks.'%name)Print('%s eating Noodles'%name) kz.release () m.release ()

There is a deadlock in the different threads that are just going to operate on the two data.
4, Signal volume

1 Import Time2 ImportRandom3  fromThreadingImportThread4  fromThreadingImportSemaphore5 deffunc (N,sem):6 Sem.acquire ()7     Print('thread-%s Start'%N)8 Time.sleep (Random.random ())9     Print('thread-%s done'%N)Ten sem.release () OneSEM = Semaphore (5)#a lock with 5 keys . A  forIinchRange (20): -Thread (target=func,args=(I,sem)). Start () - #What is the difference between the semaphore and the thread pool?  the #The same point, after the semaphore acquire, is executed at the same time as the thread pool with only n - #different points -     #the number of threads in the thread pool is a total of 5 thread semaphores. There are several tasks to open several threads - #can you execute many threads at the same time for a semaphore-constrained program?  + #In fact, the semaphore does not affect the concurrency of the thread or process, only the traffic limit during the lock-in phase

5, Event

Import TimeImportRandom fromThreadingImportEvent fromThreadingImportThreaddefConn_mysql ():#connecting to a databaseCount = 1 while  notE.is_set ():#executes the statement within the loop when the flag of the event is False        ifCount>3:            RaiseTimeouterrorPrint('attempt to connect%s times'%count) Count+ = 1e.wait (0.5)#has been blocked to become only blocking 0.5    Print('Connection Successful')#receive the set instruction within the Check_conn function to let flag become true jump out of the while loop, execute this sentence codedefcheck_conn ():" "detects if the database server is connected properly" "Time.sleep (Random.randint ())#time to simulate connection detectionE.set ()#the flag that tells the event that the database can connecte=Event () Check= Thread (target=check_conn) Check.start () Conn= Thread (target=conn_mysql) Conn.start ()

6, conditions

ImportThreadingdefrun (N): Con.acquire () con.wait ()#wait.    Print("run the thread:%s"%N) con.release ()if __name__=='__main__': Con= Threading. Condition ()#condition = function of lock + wait     forIinchRange (10): T= Threading. Thread (Target=run, args=(i,)) T.start () whileTRUE:INP= Input ('>>>')        ifINP = ='Q':             BreakCon.acquire ()#the lock in the condition is a recursive lock        ifINP = =' All': Con.notify_all ()Else: con.notify (int (INP))#Transmit signal Notify (1)-can release a threadCon.release ()

7, Timer

 from Import Timer def Hello ():         Print ("Hello,world")  while True:    #  every once in a while to open a thread    t = timer (ten, Hello)   #  timed to open a thread, perform a task                       #  timing: How long after the unit is S                      #  the task to perform: function name    t.start ()

8, queue

ImportQUEUEPQ= Queue. Priorityqueue ()#The smaller the value, the higher the value, the lower the ASC code, the first outPq.put (1,'Z')) Pq.put (1,'b')) Pq.put (15,'C')) Pq.put (2,'D'))#Print(Pq.get ())Print(Pq.get ())

9,concurrent with thread pools and callback functions

Import TimeImportRandom fromConcurrentImportFuturesdeffuncname (n):Print(n) time.sleep (Random.randint (1,3))    returnN'*'defCall (args):Print(Args.result ()) Thread_pool= Futures. Threadpoolexecutor (5)#thread PoolThread_pool.map (Funcname,range (10))#map, which is inherently asynchronous, receives data from an iterative object and does not support return valuesF_lst = [] forIinchRange (10): F= Thread_pool.submit (funcname,i)#submit incorporates the ability to create thread objects and startf_lst.append (f) thread_pool.shutdown ()#Close () join () forFinchF_lst:#must be in the order of the results    Print(F.result ())#F.result () block, etc. f execution results obtained#callback function Add_done_callback (name of callback function)Thread_pool.submit (funcname,1). Add_done_callback (Call)

Python: Thread Advanced