If I understand your code correctly, you've hardcoded the speed of your keying ("-" if duration > 150 else "."), which is probably the only realistic way to do

If I understand your code correctly, you've hardcoded the speed of your keying ("-" if duration > 150 else "."), which is probably the only realistic way to do it without getting into some really involved decoding. Have you considered using an iambic paddle? It would be a lot easier to decode I imagine, because you already know the dits and dahs from which contact is pressed.