Exactly! class Profile: ... class User: @classmethod def from_profile(cls, profile: Profile) -> 'User': ... def to_profile(sel

Exactly! class Profile: ... class User: @classmethod def from_profile(cls, profile: Profile) -> 'User': ... def to_profile(self) -> Profile: ... ...are about all the methods I need in my data records. Three simple rules though: 1. Keep isomorphisms to one class only: Don't put two def to_${OTHER_MODEL_NAME} in each class, instead (like you said) create one static mapping (@classmethod) and one instance mapping 2. Add a mapping to the one class that feels more generalized out of the two: A more generalized data model will probably be used a lot more throughout the application 3. The creation of instances should be pure: If a mapping has side effects and needs to await something then it isn't just a mapping - first resolve all necessary dependencies, then do the mapping