'fun test'

from multiprocessing.pool import Pool
import time



if __name__ == '__main__':

    print('multiprocessing test ==============')

    def ppfun(id):
        print('proc(%d) start' %id)
        time.sleep(2)
        print('proc(%d) end' %id)
        return str(id) + 'done'

    p = Pool(processes = 3)
    results = []
    for i in range(4):
        results.append(p.apply_async(ppfun, args = (i,)))
    p.close()
    p.join()
    for res in results:
        print(type(res))
        print(res.get())
    print('process(es) all done')


    print('FIN')

以上代码，apply_async()的执行函数参数ppfun在

if __name__ == '__main__':

中定义，执行时会报异常:

AtrributeError: Can't get atrribute 'ppfun' on <module '__mp_main__' from 'E:\\...\\....\\funtest.py'>

ppfun如果定义在

if __name__ == '__main__':

外面就可以正常执行。

问下这是为啥？