```
class Solution(object):
def lengthOfLastWord(self, s):
"""
:type s: str
:rtype: int
"""
if len(s)==0:
return 0
i=len(s)-1
n=0
m=0
while s[i]==' ' and i>0:
i=i-1
m=m+1
while n<len(s)-m and s[i]!=' ':
i=i-1
n=n+1
return n
```