SQLAlchemy AttributeError: 'Query' object has no attribute '_sa_instance_state' when retrieving from database

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。我想要的基本上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）以获取页面时，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

这是给我带来麻烦的代码部分。调试器指向倒数第二行（选项对象）。

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 Query，而不是 Question。你可能想要：

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

或

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

您还可以在 Question 上添加反向引用，这样您就可以从 Poll 转到 Question:

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

qinst = pinst.question

SQLAlchemy AttributeError: 'Query' object has no attribute '_sa_instance_state' when retrieving from database

SQLAlchemy AttributeError: 'Query' object has no attribute '_sa_instance_state' when retrieving from database

python

mysql

sqlalchemy

pyramid