• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

class Solution:
def reverseWords(self, s):
　　if s is None or s == ‘‘:
　　return ‘‘

　　temp_list = s.split()
　　t = ‘‘
　　for i in range(len(temp_list)-1, -1, -1):
　　　　t += temp_list[i]
　　　　t += ‘ ‘

　　t = t[:len(t)-1]
　　return t

if __name__ == ‘__main__‘:
　　a = Solution()
　　print a.reverseWords(‘the sky is blue‘)