the session.commit() method expires all attributes by default: https://docs.sqlalchemy.org/en/13/orm/session_basics.html#committing
your code is organized in an unusual way such that transactions are being committed inside of attribute assignment operations: jack.addresses.append(Address.create(session)) We can expand this out as follows: addr = jack.addresses address = Address() session.add(address) session.commit() # <--- expires all attributes on "jack", "address", invalidates "addr" attr.append(address) # <--- this is invalid, transaction was already commited I would strongly advise keeping session scope manage external to the set of operations you are performing. See https://docs.sqlalchemy.org/en/13/orm/session_basics.html#when-do-i-construct-a-session-when-do-i-commit-it-and-when-do-i-close-it for guidelines. On Wed, Feb 3, 2021, at 2:27 PM, Christian Henning wrote: > I don't understand why SQLAlchemy gives me the following warning: > > SAWarning: This collection has been invalidated. > util.warn("This collection has been invalidated.") > > Here is a minimal code example: > > ----------------- > ----------------- > > import sqlalchemy > print(sqlalchemy.__version__) > > from sqlalchemy import create_engine > from sqlalchemy import Column, Integer, ForeignKey > > from sqlalchemy.exc import IntegrityError > from sqlalchemy.ext.declarative import declarative_base > > from sqlalchemy.orm import relationship > from sqlalchemy.orm import sessionmaker > > Base = declarative_base() > > class ModelBase: > > @classmethod > def create(cls, session, **kwargs): > obj = cls(**kwargs) > session.add(obj) > session.commit() > > return obj > > > class User(ModelBase, Base): > __tablename__ = 'users' > > id = Column(Integer, primary_key=True) > > addresses = relationship("Address", order_by="Address.id", > back_populates="user") > > class Address(ModelBase, Base): > __tablename__ = 'addresses' > > id = Column(Integer, primary_key=True) > > user_id = Column(Integer, ForeignKey('users.id')) > > user = relationship("User", back_populates="addresses") > > > engine = create_engine('sqlite:///:memory:', echo=False) > Base.metadata.create_all(engine) > > Session = sessionmaker(bind=engine) > session = Session() > > jack = User.create(session) > jack.addresses.append(Address.create(session)) > > ----------------- > ----------------- > I have tested the code with SQLAlchemy for 1.3.18 and 1.4.0b1. I'm using > python 3.9.1 > > When I rewrite the last few lines a bit the warning disappears. For instance: > > jack = User.create(session) > a = Address.create(session) > jack.addresses.append(a) > > > Any insight is appreciated. I'm still learning. > > Thanks, > Christian > > > > -- > 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. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/7a369ff7-659c-4ee4-a8d0-a786ec3579aen%40googlegroups.com > > <https://groups.google.com/d/msgid/sqlalchemy/7a369ff7-659c-4ee4-a8d0-a786ec3579aen%40googlegroups.com?utm_medium=email&utm_source=footer>. -- 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. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/f16f3de5-b48d-4c89-9ebf-2430e65c579f%40www.fastmail.com.