Как проанализировать рынок фотостудий с помощью Python (2/3). База данных

from sqlalchemy import create_engine, Column, REAL, TEXT
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

engine = create_engine('sqlite:///data.db')
Base = declarative_base()
Session = sessionmaker(bind=engine)


class Item(Base):
    __tablename__ = 'items'
    url = Column(TEXT, primary_key=True)
    title = Column(TEXT)
    old_price = Column(REAL)
    price = Column(REAL)

    def __init__(self, url: str, title: str, old_price: float, price: float) -> None:
        self.url = url
        self.title = title
        self.price = price
        self.old_price = old_price

    def __repr__(self):
        return f'<Item {self.title}>'


class SQLAlc(object):
    def __init__(self):
        self.__session = Session()

    def add_item(self, item):
        self.__session.add(item)
        self.__session.commit()
        return item

    def create_if_not_exist(self, item):
        exist = self.__session.query(Item).filter_by(url=item.url).first()
        if exist:
            return None
        else:
            self.add_item(item)
            return item

    def __del__(self):
        self.__session.close()


def init_db():
    Base.metadata.create_all(bind=engine)