SQLAlchemy AttributeError:从数据库检索时,'Query'对象没有属性'_sa_instance_state'

Question

问题是尝试使用Pyramid上的SQLAlchemy从数据库中检索具有关系的对象.我想要的主要是创建我需要从数据库中检索的对象,以完成网页所需的数据.

当我尝试访问url/poll/{id}(使用有效的轮询ID,例如:/ poll/1)来获取页面时,我收到此错误:AttributeError:'Query'对象没有属性'_sa_instance_state'.怎么了？

这是模型的相关部分:

class Question(Base):
    __tablename__ = 'question'
    id = Column(Integer, primary_key=True)
    text = Column(String(250))
    type_id = Column(Integer, ForeignKey('type.id'))
    type = relationship(Type)
    poll_id = Column(Integer, ForeignKey('poll.id'))
    poll = relationship(Poll)

    def __init__(self, text, type, poll):
        self.text = text
        self.type = type
        self.poll = poll


class Option(Base):
    __tablename__ = 'option'
    id = Column(Integer, primary_key=True)
    text = Column(String(250))
    question_id =  Column(Integer, ForeignKey('question.id'))
    question = relationship(Question)

    def __init__(self, text, question):
        self.text = text
        self.question = question

这是代码中给我带来麻烦的一部分.调试器指向倒数第二行(Option对象).

if request.matchdict['id'] != None:
            pinst = session.query(Poll).get(request.matchdict['id'])
            typeq = session.query(Type).first()
            qinst = session.query(Question).filter_by(poll=pinst)
            lopt = session.query(Option).filter_by(question=qinst)
            return {'question':qinst, 'arroptions':lopt, 'type':typeq}

提前致谢!

Answer 1

qinst是一个Query,而不是一个Question.你可能想要:

qinst = session.query(Question).filter_by(poll=pinst).one()

要么

qinst = session.query(Question).filter_by(poll=pinst).first()

您还可以在添加backref Question这样你就可以从去Poll到Question:

class Question(Base):
    ...
    poll = relationship(Poll, backref="question")

qinst = pinst.question