I think it's easier to explain in an example than for me to waffle on
trying to explain myself :)
from sqlalchemy import Column, ForeignKey, Integer, create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, Session
Base = declarative_base()
class A(Base):
__tablename__ = "a"
id = Column(Integer, primary_key=True)
bs = relationship("B", backref='a')
class B(Base):
__tablename__ = "b"
id = Column(Integer, primary_key=True)
a_id = Column(Integer, ForeignKey('a.id'))
e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)
s = Session(e, autoflush=False, autocommit=True)
a1 = A()
b1 = B()
b2 = B()
b3 = B()
a1.bs.append(b1)
s.add(a1)
s.flush()
a1.bs.append(b2)
s.expire_all()
b3.a = a1
assert(b3 in a1.bs) # Yep, as you might expect
b2.a = a1
assert(b2 in a1.bs) # Nope
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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