Return type of item id from session.exec is int | None. How can I make it int.

[jd-solanki]

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Example Code

from sqlalchemy.exc import NoResultFound
from sqlmodel import Field, Session, SQLModel, create_engine

sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


class Person(SQLModel):
    id: int | None = Field(default=None, primary_key=True, index=True)
    name: str


def add_person():
    with Session(engine) as session:
        john = Person(name="John")
        session.add(john)
        session.commit()


def get_person_or_404(id: int) -> Person:
    with Session(engine) as session:
        person = session.get(Person, id)

        if not person:
            raise NoResultFound("Person not found")

        return person


def main():
    create_db_and_tables()
    add_person()
    person = get_person_or_404(1)
    print(f"person.id: {person.id}")


if __name__ == "__main__":
    main()

Description

If get person from db and db always returns the person with the id (type: int). However person returned by person = get_person_or_404(1) has person with id optional.

Hence, the type of person.id is int | None even though it is returned from DB.

How I type the get_person_or_404 function to let it know that id from Person class is int and not int | None.

Thanks.

Operating System

Linux

Operating System Details

Ubuntu 21.10

SQLModel Version

0.0.6

Python Version

3.10.2

Additional Context

[jd-solanki]

As of now, I am creating a new class and cast the return value:

def get_product(session: Session, id: PositiveInt) -> ProductDbRead | None:
    return cast(ProductDbRead, session.get(Product, id))

[YuriiMotov]

Yes, creating a separate model with required id field is a conventional approach.

class PersonBase(SQLModel):
    name: str

class Person(PersonBase):
    id: int | None = Field(default=None, primary_key=True, index=True)

class PersonRead(PersonBase):
    id: int

...

def get_person_or_404(id: int) -> PersonRead:
    with Session(engine) as session:
        person = session.get(Person, id)

        if not person:
            raise NoResultFound("Person not found")

        return PersonRead.model_validate(person, from_attributes=True)

This is explained here: https://sqlmodel.tiangolo.com/tutorial/fastapi/multiple-models/
More specifically: https://sqlmodel.tiangolo.com/tutorial/fastapi/multiple-models/#the-heropublic-data-model