python的logging问题请教

Question

代码：

# /usr/bin/python
#coding:utf-8
__author__ = 'eyu Fanne'

import multiprocessing,time
import logging

logger = logging.getLogger('mylogger')
logger.setLevel(logging.DEBUG)
fh = logging.FileHandler('test.log')
fh.setLevel(logging.DEBUG)
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
fh.setFormatter(formatter)
ch.setFormatter(formatter)
logger.addHandler(fh)
logger.addHandler(ch)

def fun(msg):

    time.sleep(2)
    print 'msg:',msg
    return 'msg:',msg
    #print 'end'

def test():
    pool = multiprocessing.Pool(processes=4)
    for i in xrange(10):
        msg = 'hello %d' %(i)
        pool.apply_async(fun,(msg,))
        #pool.apply(fun,(msg,))

    pool.close()
    pool.join()


if __name__=='__main__':
    logger.info(test())
    logger.info('dddd')

打印的结果：

msg:msg: hello 3
msg: hello 0
 hello 2
msg: hello 1
msg: hello 5
msg:msg:msg:  hello 4hello 7 
hello 6

msg: hello 8
msg: hello 9
2016-01-12 18:44:27,251 - mylogger - INFO - None
2016-01-12 18:44:27,251 - mylogger - INFO - dddd

第一个函数为何打印出来的是None的

Answer 1

因为test()没有返回值