python - can't insert into one-to-many relationship in sqlalchemy -

i have 1 many relationship in sqlalchemy don't inserts work properly. have tried make minimal example here:

from sqlalchemy import * sqlalchemy.ext.declarative import declarative_base sqlalchemy.orm import relationship, sessionmaker  db = create_engine('sqlite://') db.echo = true  metadata = metadata(db) base = declarative_base() session = sessionmaker(bind=db) session = session()  class child(base):     __table__ = table('child', base.metadata,         column('id', integer, primary_key=true),         column('parent_id', integer),         column('name', string(50))     )  class parent(base):     __table__ = table('parent', base.metadata,         column('id', integer, primary_key=true),         column('name', string(50))     )      children = relationship(child, primaryjoin="parent.id == child.parent_id",                             foreign_keys=[__table__.c.id])    base.metadata.create_all(db)  c = child(id=1, name="c") p = parent(id=1, name="p", children=[c]) session.add(p) session.commit() 

running gives attributeerror: 'list' object has no attribute '_sa_instance_state' session.add(p).

i tried changing classes this:

class child(base):     __tablename__ = 'child'      id = column('id', integer, primary_key=true)     parent_id = column('parent_id', integer, foreignkey('parent.id'))     name = column('name', string(50))  class parent(base):     __tablename__ = 'parent'      id = column('id', integer, primary_key=true)     name = column('name', string(50))      children = relationship(child, backref="parent") 

and works. specify parent_id foreign key there , use backref syntax. in production code parent table temporary table can't directly reference using foreignkey. whats wrong first code block , how can fixed ?

from sqlalchemy relationship api in docs:

that is, if primaryjoin condition of relationship() a.id == b.a_id, , values in b.a_id required present in a.id, “foreign key” column of relationship() b.a_id.

in example, child.parent_id required present in parent.id. "foreign key" column child.parent_id.

therefore, changing:

foreign_keys=[__table__.c.id] 

to this:

foreign_keys=[child.__table__.c.parent_id] 

should solve problem.