Python logging module is printing lines multiple times

logger is created once, but multiple handlers are created.

Create A once.

a = A()
for msg in ["hey", "there"]:
    a.p(msg)

Or change _get_logger as follow:

def _get_logger(self):
    loglevel = logging.INFO
    l = logging.getLogger(__name__)
    if not getattr(l, 'handler_set', None):
        l.setLevel(loglevel)
        h = logging.StreamHandler()
        f = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
        h.setFormatter(f)
        l.addHandler(h)
        l.setLevel(loglevel)
        l.handler_set = True
    return l  

UPDATE

Since Python 3.2, you can use logging.Logger.hasHandlers to see if this logger has any handlers configured. (thanks @toom)

def _get_logger(self):
    loglevel = logging.INFO
    l = logging.getLogger(__name__)
    if not l.hasHandlers():
        ...
    return l