On Feb 13, 2014, at 11:46 AM, Guido Winkelmann <gu...@ambient-entertainment.de> wrote:
>
>
> Am Donnerstag, 13. Februar 2014 15:46:31 UTC+1 schrieb Michael Bayer:
>
> On Feb 13, 2014, at 6:23 AM, Guido Winkelmann
> <gu...@ambient-entertainment.de> wrote:
>
> > Hi,
> >
> > Reading through the docs, I could not find out how to tell the cardinality
> > of an object of type sqlalchemy.orm.properties.RelationshipProperty, i.e.
> > whether it is one-to-many, many-to-one or many-to-many. Mostly, I just
> > need to know whether a relationship refers to just one object or a
> > collection of objects.
> >
> > Can someone help me with that?
>
> So given a class:
>
> MyClass
>
> and a relationship at the class level:
>
> MyClass.some_relationship
>
> you get at the RelationshipProperty like this:
>
> MyClass.some_relationship.property
>
> That doesn't work for me.
>
> For some reason, the relationship has the type
> sqlalchemy.orm.dynamic.AppenderBaseQuery, which has no attribute "property".
>
> Maybe that's because I'm using flask-sqlalchemy instead of just sqlalchemy
> directly?
“MyClass” is a class, not an object:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class A(Base):
__tablename__ = 'a'
id = Column(Integer, primary_key=True)
bs = relationship("B", lazy="dynamic")
class B(Base):
__tablename__ = 'b'
id = Column(Integer, primary_key=True)
a_id = Column(Integer, ForeignKey('a.id'))
configure_mappers()
print A.bs.property
>
>
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