之所以会发生这种情况，是因为默认情况下，您的logger_3也是

This happens because your logger_3 by default also propagates log events to its parent logger, the root logger.

如果您使用 basicConfig() ，则是根记录器默认情况下会附加StreamHandler，这也会导致您的消息也出现在控制台上.

If you use basicConfig(), the root logger will have a StreamHandler attached to it by default which causes your message to also end up on the console.

为防止这种情况，您可以设置logger_3.propagate = False，或仅将处理程序直接附加到根记录器(这是最常用的设置)，然后使用过滤器以控制输出的位置.

To prevent this, you can either set logger_3.propagate = False, or only attach handlers directly to your root logger (which is the most common used setup) and use logging levels and filters to control where your output goes.

仅将处理程序附加到根记录器的示例如下:

An example for only attaching your handlers to the root logger could look like this:

import logging
from logging.handlers import TimedRotatingFileHandler


format = '%(asctime)s: %(levelname)s: %(message)s'
logging.basicConfig(format=format, level=logging.INFO)
logger = logging.getLogger(__name__)

handler = TimedRotatingFileHandler('timerotate.log',
                                   when='s',
                                   interval=2,
                                   backupCount=10)
handler.setLevel(logging.DEBUG)
logging.root.addHandler(handler)

logger.info('This will end up on console and in timerotate.log')
logger.debug('This will only end up in timerotate.log')

basicInfo()将级别为INFO的StreamHandler附加到登录到stdout的根记录器-但仅级别为

basicInfo() attaches a StreamHandler with level INFO to the root logger that logs to stdout - but only messages with level INFO or higher.

然后再附加一个级别为DEBUG的处理程序，这样它将把级别为DEBUG或更高级别的每条消息记录到timerotate.log.这是一个非常简单的示例，它使用不同的日志级别来确定输出最终到达的位置-使用这种方法，您无法将特定的 only 语句发送到控制台，而不能将另一条 only 到文件.

You then attach a second handler with level DEBUG, so it will log every message with level DEBUG or higher to timerotate.log. This is a very simple example that uses different log levels to determine where output ends up - using this approach you can't send a particular statement only to the console, and a different one only to a file.

如果您需要更精细的控制，则可以例如在 extra关键字参数，在登录时使用

If you need more fine grained control, you could for example pass some data in the extra keyword argument when logging, and add a filter to any of your handlers to only emit messages that match certain criteria.

但是，如果您只是想直接从代码中控制一条特定消息应该发送到一个文件，并且只发送到该文件，那么将logger_3.propagate设置为False并使用它可能是最简单的您已经描述的设置.

But, if you simply want to be able to directly control from your code that a particular message should go to a file, and only that file, then it's probably easiest to simply set logger_3.propagate to False, and use the setup you already described.