import psycopg2
import psycopg2.extensions
import logging
class LoggingCursor(psycopg2.extensions.cursor):
    def execute(self, sql, args=None):
        logger = logging.getLogger('sql_debug')
        logger.info(self.mogrify(sql, args))
        try:
            psycopg2.extensions.cursor.execute(self, sql, args)
        except Exception, exc:
            logger.error("%s: %s" % (exc.__class__.__name__, exc))
            raise
conn = psycopg2.connect(DSN)
cur = conn.cursor(cursor_factory=LoggingCursor)
cur.execute("INSERT INTO mytable VALUES (%s, %s, %s);",
             (10, 20, 30))