Demonstration that SQLAlchemy doesn't facilitate the first bug described in http://kevinmahoney.co.uk/articles/django-orm-mistakes/

sqlalchemy_test.py

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import Column, Integer, create_engine


Base = declarative_base()


class Thing(Base):
    __tablename__ = "thing"
    id = Column(Integer, primary_key=True)
    foo = Column(Integer)
    bar = Column(Integer)


engine = create_engine('sqlite:///:memory:')
engine.echo = True

Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)


def create():
    session = Session()
    thing = Thing(foo=1, bar=1)
    session.add(thing)
    session.commit()
    set_foo(thing.id)
    thing.bar = 2
    session.commit()


def set_foo(id):
    session = Session()
    thing = session.query(Thing).get(id)
    thing.foo = 2
    session.commit()


create()
session = Session()
thing = session.query(Thing).one()
print thing.foo, thing.bar  # 2, 2

test_output.txt

2017-01-22 12:21:06,802 INFO sqlalchemy.engine.base.Engine ()
2017-01-22 12:21:06,803 INFO sqlalchemy.engine.base.Engine COMMIT
2017-01-22 12:21:06,804 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2017-01-22 12:21:06,805 INFO sqlalchemy.engine.base.Engine INSERT INTO thing (foo, bar) VALUES (?, ?)
2017-01-22 12:21:06,805 INFO sqlalchemy.engine.base.Engine (1, 1)
2017-01-22 12:21:06,805 INFO sqlalchemy.engine.base.Engine COMMIT
2017-01-22 12:21:06,806 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2017-01-22 12:21:06,807 INFO sqlalchemy.engine.base.Engine SELECT thing.id AS thing_id, thing.foo AS thing_foo, thing.bar AS thing_bar
FROM thing
WHERE thing.id = ?
2017-01-22 12:21:06,807 INFO sqlalchemy.engine.base.Engine (1,)
2017-01-22 12:21:06,808 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2017-01-22 12:21:06,809 INFO sqlalchemy.engine.base.Engine SELECT thing.id AS thing_id, thing.foo AS thing_foo, thing.bar AS thing_bar
FROM thing
WHERE thing.id = ?
2017-01-22 12:21:06,809 INFO sqlalchemy.engine.base.Engine (1,)
2017-01-22 12:21:06,810 INFO sqlalchemy.engine.base.Engine UPDATE thing SET foo=? WHERE thing.id = ?
2017-01-22 12:21:06,810 INFO sqlalchemy.engine.base.Engine (2, 1)
2017-01-22 12:21:06,810 INFO sqlalchemy.engine.base.Engine COMMIT
2017-01-22 12:21:06,811 INFO sqlalchemy.engine.base.Engine UPDATE thing SET bar=? WHERE thing.id = ?
2017-01-22 12:21:06,811 INFO sqlalchemy.engine.base.Engine (2, 1)
2017-01-22 12:21:06,811 INFO sqlalchemy.engine.base.Engine COMMIT
2017-01-22 12:21:06,812 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2017-01-22 12:21:06,813 INFO sqlalchemy.engine.base.Engine SELECT thing.id AS thing_id, thing.foo AS thing_foo, thing.bar AS thing_bar
FROM thing
2017-01-22 12:21:06,813 INFO sqlalchemy.engine.base.Engine ()
2 2