SQL If THEN

Hi all.

I was wondering if somenone can help me.
I needed to do a cursor.execute of a function writen in sql.
The function is:
cursor.execute("""BEGIN
            IF (TG_OP = 'UPDATE') THEN
            select NEW.test;
            RETURN NEW;
            END IF;
        END;)""")

I always get an error message saying ProgrammingError: syntax error at or near "IF"
is there a way to execute this function inside a python script?

Thanks!