python – SQLAlchemy关系错误：对象没有属性’c’

obj = session.query(Venue).filter(Venue.symbol=="CARNEGIE_HALL").one()

出于某种原因,我不断收到此错误消息：

File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/relationships.py",line 331,in _annotate_present_fks
          secondarycols = util.column_set(self.secondary.c)
      AttributeError: 'Event' object has no attribute 'c'

如果我注释掉关系定义,那么上面的查询就可以了. sqlautocode生成的关系定义看起来对我来说,但我是SqlAlchemy的新手.我不知道如何解决这个问题.我尝试从relation()更改为relationship()但我仍然得到相同的错误.

使用sqlalchemy 0.8.2和sqlautocode 0.6.

请注意,Event和Event_Type之间存在多对一关系,Event和Venue之间存在多对一关系.

model.py

DeclarativeBase = declarative_base()
metadata = DeclarativeBase.metadata
metadata.bind = engine

Event = Table(u'Event',metadata,Column(u'id',INTEGER(),primary_key=True,nullable=False),Column(u'venue_id',ForeignKey('Venue.id'),Column(u'event_type_id',ForeignKey('Event_Type.id'),)

Venue = Table(u'Venue',ForeignKey('Obj.id'),Column(u'venue_type_id',ForeignKey('Venue_Type.id'),Column(u'name',VARCHAR(length=100),Column(u'symbol',VARCHAR(length=50),)

class Event(DeclarativeBase):
    __table__ = Event


    #relation definitions
    Event_Type = relation('EventType',primaryjoin='Event.event_type_id==EventType.id')
    Venue = relation('Venue',primaryjoin='Event.venue_id==Venue.id')


class EventType(DeclarativeBase):
    __tablename__ = 'Event_Type'

    __table_args__ = {}

    #column definitions
    code = Column(u'code',nullable=False)
    description = Column(u'description',VARCHAR(length=250))
    id = Column(u'id',nullable=False)
    name = Column(u'name',nullable=False)

    #relation definitions
    Venues = relation('Venue',primaryjoin='EventType.id==Event.event_type_id',secondary=Event,secondaryjoin='Event.venue_id==Venue.id')


class Venue(DeclarativeBase):
    __table__ = Venue


    #relation definitions
    Event_Types = relation('EventType',primaryjoin='Venue.id==Event.venue_id',secondaryjoin='Event.event_type_id==EventType.id')

错误日志

mod_wsgi (pid=10861): Exception occurred processing WSGI script '/home/uname/web/html/foo/app/main.py'.
  Traceback (most recent call last):
    File "/home/uname/web/html/foo/app/main.py",line 208,in application
      return callback(environ,start_response)
    File "/home/uname/web/html/foo/app/main.py",line 68,in monitor
      obj = session.query(Venue).filter(Venue.symbol=="CARNEGIE_HALL").one()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/session.py",line 1106,in query
      return self._query_cls(entities,self,**kwargs)
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/query.py",line 115,in __init__
      self._set_entities(entities)
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/query.py",line 124,in _set_entities
      self._set_entity_selectables(self._entities)
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/query.py",line 157,in _set_entity_selectables
      ent.setup_entity(*d[entity])
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/query.py",line 2728,in setup_entity
      self._with_polymorphic = ext_info.with_polymorphic_mappers
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/util/langhelpers.py",line 614,in __get__
      obj.__dict__[self.__name__] = result = self.fget(obj)
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/mapper.py",line 1426,in _with_polymorphic_mappers
      configure_mappers()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/mapper.py",line 2121,in configure_mappers
      mapper._post_configure_properties()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/mapper.py",line 1243,in _post_configure_properties
      prop.init()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/interfaces.py",line 231,in init
      self.do_init()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/properties.py",line 1028,in do_init
      self._setup_join_conditions()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/properties.py",line 1102,in _setup_join_conditions
      can_be_synced_fn=self._columns_are_mapped
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/relationships.py",in __init__
      self._annotate_fks()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/relationships.py",line 311,in _annotate_fks
      self._annotate_present_fks()
    File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/relationships.py",in _annotate_present_fks
      secondarycols = util.column_set(self.secondary.c)
  AttributeError: 'Event' object has no attribute 'c'