import difflib a=\'abcd\' b=\'ab123\' seq=difflib.SequenceMatcher(a=a.lower(),b=b.lower()) seq=difflib.SequenceMatcher(a,b) d=seq.ratio()*100 print d
You forgot the first parameter to SequenceMatcher.
>>> import difflib >>> >>> a='abcd' >>> b='ab123' >>> seq=difflib.SequenceMatcher(None, a,b) >>> d=seq.ratio()*100 >>> print d 44.4444444444
http://docs.python.org/library/difflib.html