I have this python copy directory:

{128: ['S', 'S', 'O', 'F'], 512: ['S', 'F']}

I would like to be sure that each key has exactly one value 'F' and one value 'S' and return a message if it's not the case

I tried this but it didn't seem to work: it didn't print the message

for key in d:
    if not re.search(r"[F]{1}","".join(d[key])) or not re.search(r"[S].{1}","".join(d[key])):
        print(f"There is no start or end stop for the line {i}.")

Thanks in advance