python logging ensure a handler is added only once

I have a piece of code that is initializing a logger as below.

logger = logging.getLogger()
hdlr = logging.FileHandler('logfile.log')
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
hdlr.setFormatter(formatter)
logger.addHandler(hdlr) 
logger.setLevel(logging.DEBUG)

Unfortunately this code is being called multiple times, is there any way I can check to see if the handler already exists - I'd prefer to implement this without having to use a Singleton.

EDIT: Sorry, forgot to mention this is on python 2.5 - cheers, Richard