Michael,
>
> > class PressRoutingPress(Base):
> > '''This class defines the many-to-many join table between press
> > and press_routing.
> > '''
> > __tablename__ = "press_routing_press"
> > __table_args__ = {'autoload' : True}
> >
> > press_id = Column(Integer, ForeignKey('press.id'),
> > primary_key=True)
> > press_routing_id = Column(Integer,
ForeignKey('press_routing.id'),
> > primary_key=True)
> >
> > class PressRouting(Base):
> > '''This class defines the press_routing table information.
> > '''
> > __tablename__ = "press_routing"
> > __table_args__ = {'autoload' : True}
> >
> > class Press(Base):
> > '''This class defines the press table information.
> > '''
> > __tablename__ = "press"
> > __table_args__ = {'autoload' : True}
> >
> > # many to many Press<->PressRouting
> > press_routing = relation('PressRouting',
> > secondary=PressRoutingPress,
> >
> > primaryjoin=id==PressRoutingPress.press_id,
> >
> foreign_keys=[PressRoutingPress.press_id],
> >
> > secondaryjoin=PressRouting.id==PressRoutingPress.press_routing_id,
> >
> > foreign_keys=[PressRoutingPress.press_routing_id],
> > uselist=False)
> > #backref=backref('press'))
> > #viewonly=True)
> >
> > This all works till I try to instantiate an instance of a Press()
> > object, then I get the following exception:
>
> when you use the "secondary" argument on relation(), that should be a
> plain Table object and should not be mapped (i.e. there should be no
> separate class for it):
>
> press_routing_press = Table("press_routing_press", Base.metadata,
> Column("press_id", Integer, ForeignKey('press.id'),
> primary_key=True),
> Column("press_routing_id", Integer,
> ForeignKey('press_routing.id'),primary_key=True)
> )
>
> class Press(Base):
> ...
>
> press_routing = relation("PressRouting",
> secondary=press_routing_press)
>
> no other arguments to relation() are needed.
>
> If you do want PressRoutingPress to be mapped, you use the association
> object pattern, which means you aren't using the "secondary" keyword.
> The non-declarative version is here:
>
http://www.sqlalchemy.org/docs/05/mappers.html#advdatamapping_relation_
> patterns_association
>
I implemented your suggestion and that cleared things right up, and made
the set up code much simpler. Thanks for your help, considering how much
time you spend answering questions, I really appreciate your attention
to my issues!
Thanks again,
Doug
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