curr_msql.execute('''SELECT scode, sname sunits FROM subject_table''')

 for row in curr_msql:
            curr_pgsql.execute('''INSERT INTO subject (created, modified, code, name, units)
            SELECT current_timestamp, current_timestamp, %s, %s, %s
            WHERE NOT EXISTS(SELECT code FROM subject WHERE code = code)
            ''', (row['scode'], row['sname'], row['sunits']))

WHERE NOT EXISTS(SELECT code FROM subject WHERE code = code)

WHERE NOT EXISTS(SELECT FROM subject WHERE code IS NOT NULL)

'''INSERT INTO subject (created, modified, code, name, units)
   SELECT current_timestamp, current_timestamp, %s, %s, %s
   WHERE NOT EXISTS(SELECT code FROM subject WHERE code = %s)'''
, (row['scode'], row['sname'], row['sunits'], row['scode']))