models.py

from sqlalchemy import Column, Integer, String, Date, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.orm import declarative_base 
from sqlalchemy import Float

Base = declarative_base()

class Publisher(Base):
    __tablename__ = 'publisher'

    id = Column(Integer, primary_key=True)
    name = Column(String)
class Book(Base):
    __tablename__ = 'book'
    id = Column(Integer, primary_key=True)
    title = Column(String)
    id_publisher = Column(Integer, ForeignKey('publisher.id'))

    publisher = relationship('Publisher', backref='books')


class Shop(Base):
    __tablename__ = 'shop'

    id = Column(Integer, primary_key=True)
    name = Column(String)   

class Stock(Base):
    __tablename__ = 'stock'
    id = Column(Integer, primary_key=True)
    id_book = Column(Integer, ForeignKey('book.id'))
    id_shop = Column(Integer, ForeignKey('shop.id'))
    count = Column(Integer)

    book = relationship('Book', backref='stock')
    shop = relationship('Shop', backref='stock')
class Sale(Base):
    __tablename__ = 'sale'
    id = Column(Integer, primary_key=True)
    price = Column(Float)  
    date_sale = Column(Date)
    id_stock = Column(Integer, ForeignKey('stock.id'))
    count = Column(Integer)

    stock = relationship('Stock', backref='sales')