import re


def fillInLetters(word, letter, word_attempt):
    """
    Takes in a word_attempt and fills in any blanks with the
    inputted letter.
    Returns List of String.
    """
    indicesOfLetter = [m.start() for m in re.finditer(letter, word)]
    ret = [letter if i in indicesOfLetter else x for i, x in enumerate(word_attempt)]
    return ret