def letterMatch(letter, alphalist, letterlist, hanglist):
    """Hangman letter test with logic for no retries of prior submitted letters.
       Return True if match, False if no match, or None if invalid letter."""

    ch = letter[0] if (str == type(letter)) and (0 < len(letter)) else None

    fmatch = None
    if (None != ch) and (ch in alphalist):
        fmatch = False
        alphalist.remove(ch)
        for k in range(0, len(letterlist)):
            if ch == letterlist[k]:
                fmatch = True
                hanglist[k] = ch

    return fmatch