Perfect! Works great. Thanks for the help. -Dave
On Feb 7, 8:51 pm, Michael Bayer <mike...@zzzcomputing.com> wrote: > On Feb 7, 2012, at 3:31 PM, Dave wrote: > > > I've got a class Keyword that is many to many to itself through a > > mapped association table. The association table tracks which keyword > > is a parent of through the keywords ids (PK). Please see the pastebin. > > >http://pastebin.com/774YmjKD > > > I have been reading the <a href="http://docs.sqlalchemy.org/en/latest/ > > orm/relationships.html#sqlalchemy.orm.relationship">many to many</a> > > and <a href="http://docs.sqlalchemy.org/en/latest/orm/extensions/ > > associationproxy.html">association proxy</a> documentation but can't > > figure out how to get sqlalchemy to do what I want. > > the association proxy can be given any attribute name to point towards. your > example gets a little murky when you're trying to mix the usage of > "secondary/viewonly" along with an association object, so below is a > simplification that produces a smooth interface between Keywords: > > from sqlalchemy import * > from sqlalchemy.orm import * > from sqlalchemy.ext.declarative import declarative_base > from sqlalchemy.ext.associationproxy import association_proxy > > Base= declarative_base() > > class Keyword(Base): > __tablename__ = "keywords" > id = Column(Integer, primary_key=True, autoincrement=True) > > parents = association_proxy('parent_relations', 'pkeyword', > creator=lambda p:Relation(p, None)) > children = association_proxy('child_relations', 'ckeyword', > creator=lambda c:Relation(None, c)) > > class Relation(Base): > __tablename__ = "relations" > > def __init__(self, p, c): > self.pkeyword = p > self.ckeyword = c > > parent = Column(Integer, ForeignKey('keywords.id', ondelete="CASCADE"), > primary_key=True) > rcw = Column(Integer, ForeignKey('keywords.id', ondelete="CASCADE"), > primary_key=True) > > pkeyword = relationship("Keyword", > primaryjoin="Relation.parent==Keyword.id", > backref=backref("child_relations", > collection_class=set)) > ckeyword = relationship("Keyword", primaryjoin="Relation.rcw==Keyword.id", > backref=backref("parent_relations", > collection_class=set)) > > k1, k2, k3, k4 = Keyword(), Keyword(), Keyword(), Keyword() > k1.parents.update([k3, k4]) > k2.children.update([k1, k3]) > > assert k1.parents == set([k2, k3, k4]) > assert k2.parents == set([]) > assert k3.parents == set([k2]) > assert k4.children == set([k1]) -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
