SQLalchemy AttributeError：'str'对象没有属性'_sa_instance_state'

Question

我正在尝试使用SQLAlchemy + Python将一个项目添加到我的数据库中，但始终出现错误。

我的database_setup.py：

class company(Base):
    __tablename__ = 'company'
    compID = Column(Integer, primary_key = True)
    name = Column(String(80), nullable = False)

class item(Base):
    __tablename__ = 'items'
    itemID = Column(Integer, primary_key = True)
    name = Column(String(80), nullable = False)
    category = Column(String(250))
    description = Column(String(250))
    price = Column(String(8))
    compID = Column(Integer, ForeignKey('company.compID'))
    company = relationship(company)

在将sqlalchemy导入到终端后，我定义了一个要插入的项目：

JawboneUP3 = item(
    itemID="1",
    name="Jawbone UP3",
    description="The latest UP!", 
    category="tracker",
    price="$174.99",
    company="Jawbone"
)

并绘制一个会话以添加和提交：

session.add(JawboneUP3)
session.commit()

当我提交时，我不断收到此错误：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 1399, in add
    self._save_or_update_state(state)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 1417, in _save_or_update_state
    halt_on=self._contains_state):
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/mapper.py", line 2037, in cascade_iterator
    parent_dict, visited_states, halt_on))
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/properties.py", line 932, in cascade_iterator
    get_all_pending(state, dict_)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/orm/attributes.py", line 761, in get_all_pending
   ret = [(instance_state(current), current)]
AttributeError: 'str' object has no attribute '_sa_instance_state'

我在我的公司表中添加了一个“ Jawbone”对象，我理解我的“
JawboneUP3”应该与之相关。该对象是通过我通过网络服务器脚本启用的浏览器表单正确添加的。我相信我应该能够从终端直接添加项目。

Answer 1

我认为问题在于您如何定义相关的公司架构：

JawboneUP3 = item(itemID = "1", name = "Jawbone UP3", description = "The latest UP!", 
                  category = "tracker", price = "$174.99", company = "Jawbone")
                                                           # HERE^

该item构造函数需要一个company实例，但你传递一个字符串值。修理它：

JawboneUP3 = item(itemID="1", 
                  name="Jawbone UP3", 
                  description="The latest UP!", 
                  category="tracker", 
                  price="$174.99", 
                  company=company(name="Jawbone"))