Why bother witha lock?
For many years I have travelled with my family and not bothered with locks on our suitcases. We are insured, we usually only take clothes, books and toiletries etc. in the cases and anything expensive comes as hand luggage. Don't have to remember codes or keys.
My experience of putting expensive items in the hold is that they don't get stolen but the bags end up in a different airport to your destination. And its usually these expensive items that you want/need immediately - I can buy a shirt anywhere, but if I need my laptop with data on it...............