python中的os.walk函数遍历带有中文的路径时报错如下：

 Traceback (most recent call last):
 File "/usr/lib/python2.7/threading.py", line 810, in__bootstrap_inner
   self.run()
 File "Store.py", line 79, in run
   dir_production_list =FileOperation.visitDir_walk(self.conf.sProductionInputPath , ".mp4")
 File "/home/chaoma/superboard/Store/FileOperation.py", line55, in visitDir_walk
    for root,dirs,files in os.walk(path):
 File "/usr/lib/python2.7/os.py", line 284, in walk
   if isdir(join(top, name)):
 File "/usr/lib/python2.7/posixpath.py", line 80, in join
   path += '/' + b
UnicodeDecodeError:'utf8' codec can't decode byte 0xb3 in position 1: invalid start byte

我已经加上了:

- coding:utf-8 -

import sys
reload(sys)
sys.setdefaultencoding("utf-8")
还是没用
另外我想问各位大神们一下:os.walk()中传入的路径是str类型的字符串还是unicode类型的，或者说两个类型都可以。
十分感谢，希望大神们指点一二。