models.py

from sqlalchemy import ForeignKey, Column, Integer, String, MetaData
from sqlalchemy.orm import relationship, backref
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine

convention = {
    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
}
metadata = MetaData(naming_convention=convention)

Base = declarative_base(metadata=metadata)

class Company(Base):
    __tablename__ = 'companies'
    id = Column(Integer(), primary_key=True)
    name = Column(String())
    founding_year = Column(Integer())
    freebies = relationship("Freebie", backref="company")
    devs = relationship("Dev", secondary="freebies", viewonly=True)

    def __repr__(self):
        return f'<Company {self.name}>'

    def give_freebie(self, dev, item_name, value, session):
        freebie = Freebie(
            item_name=item_name,
            value=value,
            dev_id=dev.id,
            company_id=self.id
        )
        session.add(freebie)
        session.commit()

    @classmethod
    def oldest_company(cls, session):
        return session.query(cls).order_by(cls.founding_year).first()

class Dev(Base):
    __tablename__ = 'devs'
    id = Column(Integer(), primary_key=True)
    name = Column(String())
    freebies = relationship("Freebie", backref="dev")
    companies = relationship("Company", secondary="freebies", viewonly=True)

    def __repr__(self):
        return f'<Dev {self.name}>'

    def received_one(self, item_name):
        return any(freebie.item_name == item_name for freebie in self.freebies)

    def give_away(self, dev, freebie, session):
        if freebie.dev_id == self.id:
            freebie.dev_id = dev.id
            session.commit()

class Freebie(Base):
    __tablename__ = 'freebies'
    id = Column(Integer(), primary_key=True)
    item_name = Column(String())
    value = Column(Integer())
    dev_id = Column(Integer(), ForeignKey('devs.id'))
    company_id = Column(Integer(), ForeignKey('companies.id'))

    def print_details(self):
        return f"{self.dev.name} owns a {self.item_name} from {self.company.name}"