Python logging模块重复打印？

Python logging日志模块在使用时会进行重复打印，是否代码不对？还是？
贴上代码：

logme.py:

#!/usr/bin/env python
# _*_ coding: utf-8 _*_
__author__ = 'neilsun'
import logging
import time
import sys
import os
sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

from monitorstack import settings


logger = logging.getLogger('monitorstack')
time_obj = time.gmtime()
log_time = "{year}_{month}_{day}".format(year=time_obj.tm_year,month=time_obj.tm_mon,day=time_obj.tm_mday)

def debug(msg):
    logger.setLevel(logging.DEBUG)
    debuglogger = logging.StreamHandler()
    debuglogger.setLevel(logging.DEBUG)
    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
    debuglogger.setFormatter(formatter)
    logger.addHandler(debuglogger)
    if settings.DEBUG == True:
        logger.debug(msg)
    else:
        pass

def warning(msg):
    logger.setLevel(logging.WARNING)
    warnlogger = logging.FileHandler("logs/monitorstack_%s.log" % log_time)
    warnlogger.setLevel(logging.WARNING)
    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
    warnlogger.setFormatter(formatter)
    logger.addHandler(warnlogger)
    logger.warning(msg)

def error(msg):
    logger.setLevel(logging.ERROR)
    errorlogger = logging.FileHandler("logs/monitorstack_error_%s.log" % log_time)
    errorlogger.setLevel(logging.ERROR)
    formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
    errorlogger.setFormatter(formatter)
    logger.addHandler(errorlogger)
    logger.error(msg)

test_log.py:

#!/usr/bin/env python
# _*_ coding: utf-8 _*_
__author__ = 'neilsun'
import logme,time

logme.debug('a')
logme.debug('b')
logme.debug('c')

结果：

2016-09-21 14:59:20,983 - DEBUG - a
2016-09-21 14:59:20,983 - DEBUG - b
2016-09-21 14:59:20,983 - DEBUG - b
2016-09-21 14:59:20,983 - DEBUG - c
2016-09-21 14:59:20,983 - DEBUG - c
2016-09-21 14:59:20,983 - DEBUG - c

求解