```
class Solution(object):
def isOneEditDistance(self, s, t):
lens, lent = len(s), len(t)
if abs(lens - lent) >= 2:
return False
s, t = s if lens < lent else t, t if lens < lent else s
if lens == lent:
if s == t:
return False
for i in xrange(lens):
if s[:i] + s[i+1:] == t[:i] + t[i+1:]:
return True
return False
else:
for j in xrange(len(t)):
if t[:j] + t[j+1:] == s:
return True
return False
```