How to use SequenceMatcher to find similarity between two strings?
You forgot the first parameter to SequenceMatcher.
>>> import difflib>>> >>> a='abcd'>>> b='ab123'>>> seq=difflib.SequenceMatcher(None, a,b)>>> d=seq.ratio()*100>>> print d44.4444444444
From the docs:
The SequenceMatcher class has this constructor:
class difflib.SequenceMatcher(isjunk=None, a='', b='', autojunk=True)
The problem in your code is that by doing
seq=difflib.SequenceMatcher(a,b)
you are passing a
as value for isjunk
and b
as value for a
, leaving the default ''
value for b
. This results in a ratio of 0.0
.
One way to overcome this (already mentioned by Lennart) is to explicitly pass None
as extra first parameter so all the keyword arguments get assigned the correct values.
However I just found, and wanted to mention another solution, that doesn't touch the isjunk
argument but uses the set_seqs()
method to specify the different sequences.
>>> import difflib>>> a = 'abcd'>>> b = 'ab123'>>> seq = difflib.SequenceMatcher()>>> seq.set_seqs(a.lower(), b.lower())>>> d = seq.ratio()*100>>> print d44.44444444444444