Annotate generic base class

Symonen 0
Viewed 27

I'm creating the base repository class and getting the following error:

from typing import Any, Generic, Type, TypeVar

from sqlmodel import Session, SQLModel, select

from app.models.base import BaseModel
from app.models.notification import Notification
from app.types import SQLModelType

T = TypeVar("T", bound=BaseModel)

class BaseCRUD(Generic[T]):
    def __init__(self, db: Session, model: Type[BaseModel]) -> None:
        self.db = db
        self.model = model

    def create(self, item: T) -> T:
        self.db.add(item)
        self.db.commit()
        self.db.refresh(item)

        return item

    def get(self, uuid: Any) -> T:
        statement = select(self.model).where(self.model.uuid == uuid)

        return self.db.exec(statement).one() <---- Error: Mypy: Incompatible return value type (got "BaseModel", expected "T")

How do I annotate so that mypy knows that it is an object of a subclass of BaseModel? The TypeVar and bound are made for that right? Is it a bug then?

python-typing python
1 Answers

Okay. Figured it out. I should use T to annotate a self.model like so:

class BaseCRUD(Generic[T]):
    def __init__(self, db: Session, model: Type[T]) -> None:  # <--- T instead of BaseModel
        self.db = db
        self.model = model
Symonen0
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