Length of the Longest Alphabetical Continuous Substring — Python

# Time:  O(n)
# Space: O(1)

# string
class Solution(object):
    def longestContinuousSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        result = l = 0
        for i in xrange(len(s)):
            l += 1
            if i+1 == len(s) or ord(s[i])+1 != ord(s[i+1]):
                result = max(result, l)
                l = 0
        return result