Python-сообщество

class FContragent(Base):
    __tablename__ = "f_contragent"

    id = Column(Integer, primary_key = True)
    contragent_type_id = Column(Integer, ForeignKey('contragent_type.id'), nullable = False)
    surname = Column(Unicode, nullable = False)
    name = Column(Unicode, nullable = False)
    patronymic = Column(Unicode, nullable = False)
    phone_number = Column(Unicode, nullable = False)
    comment = Column(Unicode)

    def __init__(self, contragent_type_id, surname, name, patronymic, phone_number, comment):
        self.contragent_type_id = contragent_type_id
        self.surname = surname
        self.name = name
        self.patronymic = patronymic
        self.phone_number = phone_number
        self.comment = comment

# класс таблицы юридических лиц
class UContragent(Base):
    __tablename__ = "u_contragent"

    id = Column(Integer, primary_key = True)
    contragent_type_id = Column(Integer, ForeignKey('contragent_type.id'), nullable = False)
    org_type_id = Column(Integer, ForeignKey('org_type.id'), nullable = False)
    inn = Column(Unicode, nullable = False)
    ogrn_kpp = Column(Unicode, nullable = False)
    phone_number = Column(Unicode, nullable = False)
    org_name = Column(Unicode, nullable = False)
    account = Column(Unicode, nullable = False)
    bik = Column(Unicode, nullable = False)
    cor_account = Column(Unicode, nullable = False)
    # физический адрес
    f_zip = Column(Unicode, nullable = False)
    f_country = Column(Unicode, nullable = False)
    f_district = Column(Unicode, nullable = False)
    f_city = Column(Unicode, nullable = False)
    f_street = Column(Unicode, nullable = False)
    f_street_type_id = Column(Integer, ForeignKey('street_type.id'), nullable = False)
    f_building = Column(Unicode, nullable = False)
    f_liter_type_id = Column(Integer, ForeignKey('liter_type.id'), nullable = False)
    f_corpus_type_id = Column(Integer, ForeignKey('corpus_type.id'), nullable = False)
    # юридический адрес
    u_zip = Column(Unicode, nullable = False)
    u_country = Column(Unicode, nullable = False)
    u_district = Column(Unicode, nullable = False)
    u_city = Column(Unicode, nullable = False)
    u_street = Column(Unicode, nullable = False)
    u_street_type_id = Column(Integer, ForeignKey('street_type.id'), nullable = False)
    u_building = Column(Unicode, nullable = False)
    u_liter_type_id = Column(Integer, ForeignKey('liter_type.id'), nullable = False)
    u_corpus_type_id = Column(Integer, ForeignKey('corpus_type.id'), nullable = False)
    comment = Column(Unicode)
    sum_org_name = Column(Unicode, nullable = False)

    def __init__(self, contragent_type_id, org_type_id, org_name, inn, ogrn_kpp, phone_number, account, bik, cor_account,
                 f_zip, f_country, f_district, f_city, f_street, f_street_type_id, f_building, f_liter_type_id, f_corpus_type_id,
                 u_zip, u_country, u_district, u_city, u_street, u_street_type_id, u_building, u_liter_type_id, u_corpus_type_id,
                 comment, sum_org_name):

        self.contragent_type_id = contragent_type_id
        self.org_type_id = org_type_id
        self.inn = inn
        self.ogrn_kpp = ogrn_kpp
        self.phone_number = phone_number
        self.org_name = org_name
        self.account = account
        self.bik = bik
        self.cor_account = cor_account
        self.f_zip = f_zip
        self.f_country = f_country
        self.f_district = f_district
        self.f_city = f_city
        self.f_street = f_street
        self.f_street_type_id = f_street_type_id
        self.f_building = f_building
        self.f_liter_type_id = f_liter_type_id
        self.f_corpus_type_id = f_corpus_type_id
        self.u_zip = u_zip
        self.u_country = u_country
        self.u_district = u_district
        self.u_city = u_city
        self.u_street = u_street
        self.u_street_type_id = u_street_type_id
        self.u_building = u_building
        self.u_liter_type_id = u_liter_type_id
        self.u_corpus_type_id = u_corpus_type_id
        self.comment = comment
        self.sum_org_name = sum_org_name

# класс таблицы заказа
class Order(Base):
    __tablename__ = "order"

    id = Column(Integer, primary_key = True)
    date_reception = Column(Date, nullable = False)
    contragent_type_id = Column(Integer, ForeignKey("contragent_type.id"), nullable = False)
    contragent_id = Column(Integer, """ как организовать внешний ключ для значения из разных таблиц? """)
    amount = Column(Integer, nullable = False)
    status_id = Column(Integer, ForeignKey('status.id', nullable = False)
    date_change_status = Column(Date, nullable = False)

    def __init__(self, date_reception, contragent_type_id, contragent_id, amount, status_id, date_change_status):
        self.date_reception = date_reception
        self.contragent_type_id = contragent_type_id
        self.contragent_id = contragent_id
        self.amount = amount
        self.status_id status_id
        self.date_change_status = date_change_status

from sqlalchemy.orm import relation

class Order(Base):

    ucontragent_id = Column(Integer, ForeignKey('u_contragent.id'), nullable=True)
    fcontragent_id = Column(Integer, ForeignKey('f_contragent.id'), nullable=True)
    
    ucontragent = relation(UContragent, uselist=False, backref='orders')
    fcontragent = relation(FContragent, uselist=False, backref='orders')

class Contragent(Base):

    __tablename__ = 'contragents'

    id = Column(Integer, primary_key = True)

    # общие поля для ucontragent и fcontragent

    discriminator = Column('discriminator', String(30), nullable=False)

    __mapper_args__ = {'polymorphic_on': 'Contragent.discriminator'}


class FContragent(Contractor):

    __mapper_args__ = {'inherits': Contragent,
                                       'polymorphic_identity': 'fcontragent'}

class UContragent(Contragent):

    __mapper_args__ = {'inherits': Contragent,
                                       'polymorphic_identity': 'ucontragent'}

class Order(Base):

     contragent_id = Column(Integer, ForeignKey(Contragent.id))