Python 进程池的回调函数

import os
from multiprocessing import Pool,Process

def f1(n):
    print('进程池里面的进程id',os.getpid())
    print('>>>>',n)
    return n*n

def call_back_func(asdf):
    print('>>>>>>>>>>>>>',os.getpid())
    print('回调函数中的结果:',asdf)
    # print('回调函数中的结果:',s.get())

if __name__ == '__main__':
    pool = Pool(4)
    res = pool.apply_async(f1,args=(5,),callback=call_back_func)
    pool.close()
    pool.join()
    # print(res.get())
    print('主进程的进程id',os.getpid())