It appears that the .read_only attribute of a connection is not honored when the connection is in autocommit mode.
There's no mention of this on the Connection classes page for read_only, and in the section linked to in Transactions management you have to read it 3 times to realize it's only used with Connection.transaction(). Is it the intent to not be used for regular autocommit connections, or is it an oversight? I used conn.set_session(readonly = True, deferrable = False, autocommit = True) in psycopg2, and that seemed to work at preventing accidental changes. I've just been moving to psycopg recently, and with no set_session I replaced it with putting autocommit = True in the connection call and following it with .read_only = True and .deferrable = False Since I vastly prefer autocommit mode, is my best bet then to replace conn.read_only = True with either conn.execute("set session characteristics as transaction read only, not deferrable;") or conn.execute("set default_transaction_read_only to true;") conn.execute("set default_transaction_deferrable to false;") ? (Honestly in my mind I thought this is what changing .read_only, .deferrable, or .isolation_level did in the background already) Thank you for your patience with me,