Question

class Cookie(Base):
    __tablename__ = 'cookies'

    cookie_id = Column(Integer(), primary_key=True)
    cookie_name = Column(String(50), index=True)
    cookie_recipe_url = Column(String(255))
    cookie_sku = Column(String(55))
    quantity = Column(Integer())
    unit_cost = Column(Numeric(12, 2))

    def __repr__(self): 
        return "Cookie(cookie_name='{self.cookie_name}', " \
                       "cookie_recipe_url='{self.cookie_recipe_url}', " \
                       "cookie_sku='{self.cookie_sku}', " \
                       "quantity={self.quantity}, " \
                       "unit_cost={self.unit_cost})".format(self=self)


class User(Base):
    __tablename__ = 'users'

    user_id = Column(Integer(), primary_key=True)
    username = Column(String(15), nullable=False, unique=True)
    email_address = Column(String(255), nullable=False)
    phone = Column(String(20), nullable=False)
    password = Column(String(25), nullable=False)
    created_on = Column(DateTime(), default=datetime.now)
    updated_on = Column(DateTime(), default=datetime.now,
                        onupdate=datetime.now)

    def __repr__(self):
        return "User(username='{self.username}', " \
                     "email_address='{self.email_address}', " \
                     "phone='{self.phone}', " \
                     "password='{self.password}')".format(self=self)

class Order(Base):
    __tablename__ = 'orders'
    order_id = Column(Integer(), primary_key=True)
    user_id = Column(Integer(), ForeignKey('users.user_id'))

    user =  relationship("User", backref=backref('orders', order_by=order_id))

    def __repr__(self):
        return "Order(user_id={self.user_id}, " \
                      "shipped={self.shipped})".format(self=self)

class LineItems(Base):
    __tablename__ = 'line_items'
    line_item_id = Column(Integer(), primary_key=True)
    order_id = Column(Integer(), ForeignKey('orders.order_id'))
    cookie_id = Column(Integer(), ForeignKey('cookies.cookie_id'))
    quantity = Column(Integer())
    extended_cost = Column(Numeric(12, 2))
    order = relationship("Order", backref=backref('line_items',
                         order_by=line_item_id))
    cookie = relationship("Cookie", uselist=False, order_by=id)

    def __repr__(self):
        return "LineItems(order_id={self.order_id}, " \
                          "cookie_id={self.cookie_id}, " \
                          "quantity={self.quantity}, " \
                          "extended_cost={self.extended_cost})".format(
                    self=self)

运行完以上所有语句后，我然后尝试运行此语句：

cc_cookie = Cookie(cookie_name='chocolate chip', 
                   cookie_recipe_url='http://some.aweso.me/cookie/recipe.html',
                   cookie_sku='CC01',
                   quantity=12,
                   unit_cost=0.50)

这样做，会生成此错误消息：

sqlalchemy.exc.InvalidRequestError：一个或多个映射器无法执行初始化-无法继续进行其他映射器的初始化。触发映射器：“映射类LineItems-> line_items”。原版的例外是：id（）恰好接受一个参数（给定0）

到目前为止我一直在尝试做的事情：

我查看了我的Python代码以及数据库中各个表中的所有列，所有内容均已正确键入。

有什么建议吗？我是sqlalchemy的新手。

编辑：

它肯定与LineItems类有关。

我需要更改

cookie = relationship("Cookie", uselist=False, order_by=id)

对此：

cookie = relationship("Cookie", uselist=False, order_by=line_item_id)

SQL炼金术：一个或多个映射器初始化失败-无法继续进行其他映射器的初始化。插入时产生错误

0 个答案: