How to map complex object attribute using SQLAlchemy

Question

Is there any way in SQLAlchemy to perform some kind of 'deep mapping' of the class attributes?

For instance: obj.attr.nested_attr, I'd like to tell obj mapper how to directly map nested_attr to a nested_attr column in a table.

Python: 3.10.7

SQLAlchemy: 1.4.41

Let's say we have domain model of:

@dataclass
class FullName:
    first_name: str
    last_name: str


@dataclass
class User:
    name: FullName
    date_of_birth: datetime
    etc...

And an SQLAlchemy table model like:

users = sqlalchemy.Table(
   "users",
   metadata,
   sqlalchemy.Column("first_name", sqlalchemy.String),
   sqlalchemy.Column("last_name", sqlalchemy.String),
   etc...
)

Is there any way in SQLAlchemy to map name (which is of type FullName) attributes first_name and last_name to users table columns first_name and last_name?

I tried:

mapper_registry = registry()

    mapper_registry.map_imperatively(
        User,
        users,
        properties={
            "name.first_name": users.c.first_name,
            "name.last_name": users.c.last_name,
        },
    )

However, SQLAlchemy doesn't seem to comprehend accessing attributes' of an attribute by dot notation.

Is there any other way to directly map user.name.first_name to first_name column of the users table?

Answer 1

Composite may be the solution you are looking for.