I suspect this is user error, but I am not ferreting out my mistake.
I'm porting some older code to SQLAlchemy 0.71 on top of Python 2.7.1. Code
which had originally implemented foreign keys without using REFERENCES
clauses in CREATE TABLE statements previously ran fine. Now, adding formal
foreign keys isn't working. I have boiled this down to the following
variant on the example found in the SQLAlchemy Documentation:
=====8<--------------------------------------
#!/usr/bin/env
python
from sqlalchemy import create_engine, Column, ForeignKey, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship, backref
Base = declarative_base()
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String)
fullname = Column(String)
password = Column(String)
addresses = relationship('Address', order_by='Address.id',
backref='user')
def __init__(self, name, fullname, password):
self.name = name
self.fullname = fullname
self.password = password
def __repr__(self):
return "<User('%s', '%s', '%s', '%s')>" % (self.id, self.name,
self.fullname, self.password)
class Address(Base):
__tablename__ = 'addresses'
id = Column(Integer, primary_key=True)
email_address = Column(String, nullable=False)
user_id = Column(Integer, ForeignKey('users.id'))
user = relationship('User', backref=backref('addresses', order_by=id))
def __init__(self, email):
self.email_address = email
def __repr__(self):
return "<Address('%s', '%s', '%s')>" % (self.id, self.email_address,
self.user_id)
if __name__ == '__main__':
engine = create_engine('sqlite:///:memory:', echo=True)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()
user = User('jdoe', 'John Doe', 'password')
print user
session.add(user)
session.commit()
=====8<--------------------------------------
Execution yields the following traceback:
=====8<--------------------------------------
traceback (most recent call last):
File "./test.py", line 51, in <module>
user = User('jdoe', 'John Doe', 'password')
File "<string>", line 2, in __init__
File
"/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/instrumentation.py",
line 309, in _new_state_if_none
state = self._state_constructor(instance, self)
File
"/usr/local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py",
line 432, in __get__
obj.__dict__[self.__name__] = result = self.fget(obj)
File
"/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/instrumentation.py",
line 157, in _state_constructor
self.dispatch.first_init(self, self.class_)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/event.py", line
274, in __call__
fn(*args, **kw)
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py",
line 2787, in _event_on_first_init
configure_mappers()
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py",
line 2719, in configure_mappers
mapper._post_configure_properties()
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/mapper.py",
line 1035, in _post_configure_properties
prop.init()
File
"/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/interfaces.py", line
121, in init
self.do_init()
File
"/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/properties.py", line
905, in do_init
self._generate_backref()
File
"/usr/local/lib/python2.7/site-packages/sqlalchemy/orm/properties.py", line
1376, in _generate_backref
self, mapper))
sqlalchemy.exc.ArgumentError: Error creating backref 'user' on relationship
'User.addresses': property of that name exists on mapper
'Mapper|Address|addresses'
=====8<--------------------------------------
Any insight shared would be greatly appreciated. Thanks.
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