Python NDB: what's the best way to have a Set instead of a List in property?

Question

in NDB you have repeated properties, they behave just like a native python list but i want them to behave just like native sets. i need to have a set of keys that is without duplicates. in python you can remove duplicates like the_list = list(set(the_list)),

but how would you implement this so it is automatic and i don't to think about this ?

Answer 1

Three ways come to mind:

1. enforce the list (repeated property) is unique with a "setter" method that only inserts unique values;
2. likewise, enforce the list is unique with a _pre_put_hook() method;
3. use the key on each entity as your list, ndb will make sure they are unique.