python - Finding index of characters in a string

def indexes(word, letter):

            acc=[]
 for i in word:
 for g in letter:
 if g in
            i:
 acc.append(word.index(i))
 return
            acc

if i call the
function indexes("mississippi","s") the following is
returned:

[2, 2, 2,
            2]

So, the function
returns the correct amount of letters, but it only returns the first index of where
"s" is found and fills the list with that index. Any reason why
the list doesn't return the index of each
"s"?