属性错误：'InstrumentedList'对象没有属性。

Question

我有这些桌子：

class Thing(Base):
    __tablename__ = 'thing'
    id = Column(Integer, primary_key=True)

class User(Base):
    __tablename__ = 'user'
    id = Column(Integer, primary_key=True)

class Voteinfo(Base):
    __tablename__ = 'voteinfo'
    thing_id = Column(Integer, ForeignKey('thing.id'), primary_key=True)
    thing = relationship('Thing', backref='voteinfo')
    upvotes = Column(Integer)
    downvotes = Column(Integer)

    def __init__(self, thing)
        self.thing = thing

class VoteThing(Base):
    __tablename__ = 'votething'
    id = Column(Integer, primary_key=True)
    voter_id = Column(Integer, ForeignKey('voter.id'))
    voter = relationship('Voter', backref='votescast')
    thing_id = Column(Integer, ForeignKey('thing.id'))
    thing = relationship('Thing', backref='votesreceived')
    value = Column(Boolean)

    def __init__(self, voter, thing, value):
        if value is True:
            thing.voteinfo.upvotes += 1
        else:
            thing.voteinfo.downvotes += 1

当我尝试运行此命令时，在“if value is True”子句中会得到此错误代码：

AttributeError: 'InstrumentedList' object has no attribute 'upvotes'

我试过给Voteinfo自己的唯一ID，并将uselist=False添加到关系中。我试着把与事物的关系从votesing换成Voteinfo，但这也没用。我不知道什么是工具列表。怎么回事？

Answer 1

如文档中所述，这里：https://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#one-to-one，您必须将uselist=False添加到backref，而不是添加到关系中。

thing = relationship('Thing', backref=backref('voteinfo', uselist=False))