sqlalchemy - SqlSoup relate() for many-to-many relation throwing exception -

i'm using following code use sqlsoup existing database.

import sqlalchemy sqlalchemy.ext.sqlsoup import sqlsoup sqlalchemy.orm import backref  engine = sqlalchemy.create_engine('postgresql:///test') db = sqlsoup(engine) db.books.relate('author', db.authors) db.books.relate('tags', db.tags, secondary=db.tags2books, backref=backref('books', lazy=false)) 

however, last relate() call throws exception:

traceback (most recent call last):   file "sqlsoup-test.py", line 10, in <module>     db.books.relate('tags', db.tags, secondary=db.tags2books, backref=backref('books', lazy=false))   file "/usr/lib64/python2.6/site-packages/sqlalchemy/ext/sqlsoup.py", line 384, in relate     class_mapper(cls)._configure_property(propname, relationship(*args, **kwargs))   file "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/mapper.py", line 758, in _configure_property     prop.init()   file "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/interfaces.py", line 476, in init     self.do_init()   file "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/properties.py", line 895, in do_init     self._determine_joins()   file "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/properties.py", line 1010, in _determine_joins     self.secondary)   file "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/properties.py", line 1002, in _search_for_join     return join_condition(mapper.local_table, table)   file "/usr/lib64/python2.6/site-packages/sqlalchemy/sql/util.py", line 219, in join_condition     fk in b.foreign_keys: attributeerror: 'mappedtags2books' object has no attribute 'foreign_keys' 

the tables have been created using following definition:

authors_table = table('authors', metadata,     column('id', integer, primary_key=true),     column('name', string, nullable=false, index=true) )  books_table = table('books', metadata,     column('id', integer, primary_key=true),     column('author_id', integer,         foreignkey('authors.id', onupdate='cascade', ondelete='cascade'),         nullable=false),     column('title', string, nullable=false, index=true) )  tags_table = table('tags', metadata,     column('id', integer, primary_key=true),     column('tag', string, index=true, unique=true, nullable=false) )  tags2books_table = table('tags2books', metadata,     column('tag_id', integer,         foreignkey('tags.id', onupdate='cascade', ondelete='cascade'),         primary_key=true),     column('book_id', integer,         foreignkey('books.id', onupdate='cascade', ondelete='cascade'),         primary_key=true) ) 

in case going ask "why using sqlsoup when can use real sqlalchemy?": i'm writing term paper sqlalchemy , i'm mentioning sqlsoup in 1 chapter , i'd add example. , what's easier using database i've used sa examples...

looks secondary can't mapped class. passing table fixes error:

db.books.relate('tags', db.tags, secondary=db.tags2books._table, backref=backref('books', lazy=false))