How to make a function that counts how many times each element is equal to 2 elements to its right

Question

I know i need to use a list comprehension but for the life of me I cannot figure out what would be the correct way to denote this. An example of this running right would be for

Answer 1

The list comprehension gives the letters that have the same letter two places to the right. We simply take the length of the resulting list:

s = "evening"
ans = len([x for x in xrange(len(s)-2) if s[x] == s[x+2]])
print ans