class Solution(object):
    def isOneEditDistance(self, word1, word2):
        l1=len(word1)
        l2=len(word2)
        if l1>l2:
            return self.isOneEditDistance(word2,word1)
        if l2-l1>1:
            return False
        i=0
        while i<l1 and word1[i]==word2[i]:
            i+=1 
        if l1==l2:
            return word1[i+1:]==word2[i+1:]
        else:
            return word1[i:]==word2[i+1:]