Example of adding a filter to a Logger's Handler.

Awesome example developed during my Advanced Python Training that shows how to log to a different log file based on log level

"""

Example of adding a filter to a Logger's Handler.

"""

from logging import getLogger, FileHandler, INFO, ERROR

class LogOneLevel:

  """Enables messages at one specifie level only"""

  def __init__(self, level):

      self.level = level

  def filter(self, log_record):

      return log_record.levelno == self.level

logger = getLogger('logger_demo')

info_handler = FileHandler('info.log')

info_handler.addFilter(LogOneLevel(INFO))  # add filter to handler

logger.addHandler(info_handler)

error_handler = FileHandler('error.log')

error_handler.addFilter(LogOneLevel(ERROR))  # add filter to handler

logger.addHandler(error_handler)

logger.info("info msg")    # written to info.log only

logger.error("error msg")  # written to error.log only

File-Based Configuration

1. Define a Handler subclass that adds a Filter instance to itself:

class InfoHandler(RotatingFileHandler):

   def __init__(self, *args, **kwargs):

       super().__init__(self, *args, **kwargs)

       self.addFilter(LogOneLevel(INFO))

2. Configure Handler subclass in config file:

[logger_unittestgui]

level=DEBUG

handlers=console_handler,info_handler

[handler_info_handler]

class=mypackage.mylogging.InfoHandler

formatter=file_formatter

args=('gui.log', 'a', 10000000, 5)  # passed to superclass __init__()

# http://tinyurl.com/logging-filter