@contextmanager
def transaction(connection):
    trans = connection.begin()
    try:
        yield trans
    except Exception:
        trans.rollback()
        raise
    else:
        trans.commit()


def deadlock_first():
    import time

    time.sleep(1)
    engine = sqlalchemy.create_engine('postgresql://{user}:{password}@{host}:{port}/{db}'.format(**config))
    connect = engine.connect()
    print(connect)
    sql = "select func1();"
    with transaction(connect) as trans:
        connect.execute(sql)


def deadlock_retry():
    engine = sqlalchemy.create_engine('postgresql://{user}:{password}@{host}:{port}/{db}'.format(**config))
    connect = engine.connect()
    print(connect)
    sql = "select func2();"
    try:
        with transaction(connect) as trans:
            connect.execute(sql)
    except sqlalchemy.exc.OperationalError as e:
        if "deadlock" in str(e):
            with transaction(connect) as trans:
                connect.execute(sql)


def main():
    t1 = threading.Thread(target=deadlock_first)
    t2 = threading.Thread(target=deadlock_retry)
    t1.start()
    t2.start()