Count letter differences of two strings

Question

This is the behaviour I want:

a: IGADKYFHARGNYDAA
c: KGADKYFHARGNYEAA
2 difference(s).

Answer 1

With difflib.ndiff you can do this in a one-liner that's still somewhat comprehensible:

>>> import difflib
>>> a = 'IGADKYFHARGNYDAA'
>>> c = 'KGADKYFHARGNYEAA'
>>> sum([i[0] != ' '  for i in difflib.ndiff(a, c)]) / 2
2

(sum works here because, well, kind of True == 1 and False == 0)

The following makes it clear what's happening and why the / 2 is needed:

>>> [i for i in difflib.ndiff(a,c)]
['- I',
 '+ K',
 '  G',
 '  A',
 '  D',
 '  K',
 '  Y',
 '  F',
 '  H',
 '  A',
 '  R',
 '  G',
 '  N',
 '  Y',
 '- D',
 '+ E',
 '  A',
 '  A']

This also works well if the strings have a different length.