StackOverflow 76160846

so76160846.py

# pip install SQLAlchemy==2.0.12 psycopg2==2.9.6
import random
from sqlalchemy import Column, Integer, String
from sqlalchemy import create_engine
from sqlalchemy import select
from sqlalchemy.orm import declarative_base, sessionmaker, scoped_session

Base = declarative_base()

class Entity(Base):
    __tablename__ = 'entity'
    id = Column(Integer, primary_key=True)
    field_a = Column(String(255))

def main():
    engine = create_engine('postgresql://postgres@localhost/postgres')
    Base.metadata.create_all(engine)
    Session = scoped_session(sessionmaker(bind=engine))
    session = Session()
    session_replica = Session()

    entity = session.query(Entity).first()
    entity.field_a = str(random.random())
    session.add(entity)
    session.commit()

    entity_rr = session_replica.query(Entity).filter(Entity.id == entity.id).one()  
    assert entity_rr.field_a == entity.field_a

if __name__ == '__main__':
    main()