install filter on logging level in python using dictConfig

Question

I cannot install a filter on a logging handler using dictConfig() syntax. LoggingErrorFilter.filter() is simply ignored, nothing happens.

I want to filter out error messages so that they do not appear twice in the log output. So I wrote LoggingErrorFilter class and overrode filter().

My configuration:

class LoggingErrorFilter(logging.Filter):   def filter(self, record):     print 'filter!'     return record.levelno == logging.ERROR or record.levelno == logging.CRITICAL  config = {       'version': 1,       'disable_existing_loggers' : False,       'formatters' : {         'standard' : {           'format' : '%(asctime)s %(levelname)s %(name)s::%(message)s',         },       },       'handlers' : {         'console': {           'class' : 'logging.StreamHandler',           'level' : level,           'formatter' : 'standard',           'stream' : 'ext://sys.stdout',         },         'errorconsole': {           'class' : 'logging.StreamHandler',           'level' : 'ERROR',           'formatter' : 'standard',           'stream' : 'ext://sys.stderr',           'filters'  :['errorfilter',],         },       },       'filters': {         'errorfilter': {           'class' : 'LoggingErrorFilter',         }       },       'loggers' : {         '' : {           'handlers' : ['errorconsole','console',],           'level' : level,           'propagate' : True,         },         name : {           'handlers' : ['errorconsole','console',],           'level' : level,           'propagate' : False,         },       },   }   logging.config.dictConfig(config) 

What am I doing wrong here? Why is my filter ignored?

Answer 1

Actually, Tupteq's answer is not correct in general. The following script:

import logging import logging.config import sys  class MyFilter(logging.Filter):     def __init__(self, param=None):         self.param = param      def filter(self, record):         if self.param is None:             allow = True         else:             allow = self.param not in record.msg         if allow:             record.msg = 'changed: ' + record.msg         return allow  LOGGING = {     'version': 1,     'filters': {         'myfilter': {             '()': MyFilter,             'param': 'noshow',         }     },     'handlers': {         'console': {             'class': 'logging.StreamHandler',             'filters': ['myfilter']         }     },     'root': {         'level': 'DEBUG',         'handlers': ['console']     }, }  if __name__ == '__main__':     print(sys.version)     logging.config.dictConfig(LOGGING)     logging.debug('hello')     logging.debug('hello - noshow') 

When run, produces the following output:

$ python filtcfg.py  2.7.5+ (default, Sep 19 2013, 13:48:49)  [GCC 4.8.1] changed: hello 

which shows that you can configure filters using dictConfig().

Answer 2

You can specify a class name, but it is done with the strangely named () key, and it has to include the module name. E.g.:

 'filters': {     'errorfilter': {       '()' : '__main__.LoggingErrorFilter',     }   }, 

See 16.7.2.4. User-defined objects in the documentation.