python- multi-thread synchronization mutex is created to solve the problem of resource contention

Threading Import 
Import Time 

# define a global variable 
g_num = 0 


DEF test1 (NUM): 
    Global g_num 
    for I in (NUM) Range: 
        g_num + =. 1 
    Print ( 'test1 g_num in ------- = {}'. the format (g_num)) 


DEF test2 (NUM): 
    Global g_num 
    for I in Range (NUM): 
        g_num + =. 1 
    Print ( 'test1 g_num in ------- = {}' the format (g_num.)) 


DEF main (): 
    T1 = threading.Thread (target = test1, args = (1000000,)) # test results of ten thousand output is correct, but there is a problem with one million 
    t2 = threading.Thread (target = test1 , args = (1000000,)) 

    t1.start () 
    t2.start () 

    # wait time implementation of the above two processes 
    the time.sleep (. 5) 
    Print ( '------- in the Thread main g_num = {} '.format (g_num))


__name__ == IF '__main__': 
    main () 

# The above procedure will cause resource contention problems, the results of the final output is (the result will be different each time, but certainly not our logic results)

-------in test1 g_num=1172278
-------in test1 g_num=1288801
-------in main Thread g_num=1288801

 

## solution is as follows (in red font for newly added code)

Threading Import 
Import Time 

# define a global variable 
g_num = 0 


DEF test1 (NUM): 
    , Ltd. Free Join g_num 

    for i in (NUM) the Range: 
        # locked if you have not been locked, then unlocked at this time success 
        # If a previously locked is locked, then it will clog here until the lock is solved 
        mutex.acquire ()
         g_num + =. 1 
        mutex.release ()
     Print ( 'test1 g_num in ------- = {}'. the format (g_num)) 


DEF test2 (NUM): 
    Global g_num 

    for I in Range (NUM): 
        mutex.acquire ()
         g_num + =. 1 
        mutex.release ()
     Print ( 'test1 g_num in ------- = { .} 'the format (g_num)) 


# Create a mutex, the default is unlocked 
the mutex of threading.Lock = () 


DEF main ():
    t1 = threading.Thread (target = test1, args = (1000000,)) # test results of ten thousand output is correct, but there is a problem with one million 
    t2 = threading.Thread (target = test1, args = (1000000,)) 

    t1.start () 
    t2.start () 

    # wait time implementation of the above two processes 
    the time.sleep (. 5) 
    Print ( '------- in the Thread main g_num = {}'. the format (g_num)) 


IF the __name__ == '__main__': 
    main ()