问如何在使用并行编程时更改全局变量

EN

import multiprocessing as mp

a = 3
b = 5

# define a example function
def f(length, output):
    global a
    global b
    if length==5:
       a = length + a
       output.put(a)
    if length==3:
       b = length + b
       output.put(b)


if __name__ == '__main__':

     # Define an output queue
     output = mp.Queue()    

     # Setup a list of processes that we want to run
     processes = []
     processes.append(mp.Process(target=f, args=(5, output)))
     processes.append(mp.Process(target=f, args=(3, output)))

     # Run processes
     for p in processes:
         p.start()

     # Exit the completed processes
     for p in processes:
         p.join()

     # Get process results from the output queue
     results = [output.get() for p in processes]

     print(results)
     print ("a:",a)
     print ("b:",b)

[8, 8]
a: 3
b: 5