作为@offbyone cmets，可以将冗余处理程序添加到记录器的同一实例。
python docs for logging 说-
"多次调用同名的getLogger()会返回一个
引用同一个记录器对象。”
所以我们不必担心将实现变成单例，因为它已经是。
不幸的是，与同一记录器实例关联的处理程序不正确。 可能附加了重复的处理程序。
例子-
-
复制这段代码并保存在main.py中
import logging
print 'inside main.py',
print '-'*50
def logger():
print 'initializing logger....'
logPath = '.'
fileName = 'temp'
# configure log formatter
logFormatter = logging.Formatter("%(asctime)s [%(filename)s] [%(funcName)s] [%(levelname)s] [%(lineno)d] %(message)s")
# configure file handler
fileHandler = logging.FileHandler("{0}/{1}.log".format(logPath, fileName))
fileHandler.setFormatter(logFormatter)
# configure stream handler
consoleHandler = logging.StreamHandler()
consoleHandler.setFormatter(logFormatter)
# get the logger instance
logger = logging.getLogger(__name__)
# set the logging level
logger.setLevel(logging.DEBUG)
print 'adding handlers- '
#if not len(logger.handlers):
logger.addHandler(fileHandler)
logger.addHandler(consoleHandler)
print 'logger initialized....\n'
print 'associated handlers - ', len(logger.handlers)
for handler in logger.handlers:
print handler
print
return logger
main_logger = logger()
main_logger.info('utilizing main.py logger.')
print 'exiting main.py',
print '-'*50
-
以及sub.py中的以下代码
print 'inside sub.py',
print '-'*50
print 'importing main.py'
import main
print 'imported main.py'
import logging
print 'getting logger instance in sub'
sub_logger = main.logger()
print 'got logger instance in sub'
sub_logger.info("utilizing sub_logger")
print 'exiting sub.py',
print '-'*50
-
运行 sub.py
narayan@y510p:~/code/so$ python sub.py
inside sub.py --------------------------------------------------
importing main.py
inside main.py --------------------------------------------------
initializing logger....
adding handlers-
logger initialized....
associated handlers - 2
<logging.FileHandler object at 0x7f7158740c90>
<logging.StreamHandler object at 0x7f7158710b10>
2015-08-04 07:41:01,824 [main.py] [<module>] [INFO] [41] utilizing main.py logger.
exiting main.py --------------------------------------------------
imported main.py
getting logger instance in sub
initializing logger....
adding handlers-
logger initialized....
associated handlers - 4 # <===== 4 handlers (duplicates added)
<logging.FileHandler object at 0x7f7158740c90>
<logging.StreamHandler object at 0x7f7158710b10>
<logging.FileHandler object at 0x7f7158710bd0>
<logging.StreamHandler object at 0x7f7158710c10>
got logger instance in sub
2015-08-04 07:41:01,824 [sub.py] [<module>] [INFO] [10] utilizing sub_logger
2015-08-04 07:41:01,824 [sub.py] [<module>] [INFO] [10] utilizing sub_logger
exiting sub.py --------------------------------------------------
因此，多次调用返回相同记录器的方法会添加重复的处理程序。
现在，你的问题-
有什么方法可以检查处理程序是否已经存在
是的，有-
logger.handlers 返回与给定logger 关联的所有处理程序的列表。
在将处理程序添加到记录器的实例之前，请确保不要添加重复的处理程序
在 main.py 中，取消注释 if not len(logger.handlers): 并正确缩进以下两行 -
if not len(logger.handlers):
logger.addHandler(fileHandler)
logger.addHandler(consoleHandler)
现在再次运行 sub.py
narayan@y510p:~/code/so$ python sub.py
inside sub.py --------------------------------------------------
importing main.py
inside main.py --------------------------------------------------
initializing logger....
adding handlers-
logger initialized....
associated handlers - 2
<logging.FileHandler object at 0x7fd67a891c90>
<logging.StreamHandler object at 0x7fd67a862b10>
2015-08-04 08:14:45,620 [main.py] [<module>] [INFO] [41] utilizing main.py logger.
exiting main.py --------------------------------------------------
imported main.py
getting logger instance in sub
initializing logger....
adding handlers-
logger initialized....
associated handlers - 2 # <===== Still 2 handlers (no duplicates)
<logging.FileHandler object at 0x7fd67a891c90>
<logging.StreamHandler object at 0x7fd67a862b10>
got logger instance in sub
2015-08-04 08:14:45,620 [sub.py] [<module>] [INFO] [10] utilizing sub_logger
exiting sub.py --------------------------------------------------
此外，如果您想限制要添加到记录器实例的处理程序的类型，您可以执行以下操作-
print 'adding handlers- '
# allows to add only one instance of file handler and stream handler
if len(logger.handlers) > 0:
print 'making sure we do not add duplicate handlers'
for handler in logger.handlers:
# add the handlers to the logger
# makes sure no duplicate handlers are added
if not isinstance(handler, logging.FileHandler) and not isinstance(handler, logging.StreamHandler):
logger.addHandler(fileHandler)
print 'added file handler'
logger.addHandler(consoleHandler)
print 'added stream handler'
else:
logger.addHandler(fileHandler)
logger.addHandler(consoleHandler)
print 'added handlers for the first time'
希望这会有所帮助！
编辑：
不幸的是，对于关联的处理程序，不正确
与记录器的相同实例。 可以重复
附加处理程序。
事实证明，上述说法并不完全正确。
假设我们在主模块中创建并配置了一个名为 'main_logger' 的记录器（它只是配置记录器，不返回任何内容）。
# get the logger instance
logger = logging.getLogger("main_logger")
# configuration follows
...
现在在子模块中，如果我们按照命名层次'main_logger.sub_module_logger'创建一个子记录器，我们不需要在子模块中配置它。只需按照命名层次结构创建记录器就足够了。
# get the logger instance
logger = logging.getLogger("main_logger.sub_module_logger")
# no configuration needed
# it inherits the configuration from the parent logger
...
它也不会添加重复的处理程序。
参考-Using logging in multiple modules