hackerrank alternating characters

gistfile1.txt

from itertools import groupby
import operator

def algo(string):
    s = list(string)
    g = sum(len(list(v)) -1 for (k,v) in groupby(s, key=operator.itemgetter(0)))
    return g 

num = raw_input()
cases = [] 
for case in range(int(num)):
    cases.append(raw_input())

for c in cases:
    print algo(c)