notifications-api/app/dao/__init__.py

from sqlalchemy.exc import SQLAlchemyError

from app import db


# Should I use SQLAlchemyError?
class DAOException(SQLAlchemyError):
    pass


class DAOClass(object):
    class Meta:
        model = None

    def create_instance(self, inst, _commit=True):
        db.session.add(inst)
        if _commit:
            db.session.commit()

    def delete_instance(self, inst, _commit=True):
        db.session.delete(inst)
        if _commit:
            db.session.commit()