A example of logging medium complex configuration using YAML on Python 2.7 or 3.2

logging_yaml_config.py

# -*- coding: utf-8
"""\
A simple demo of logging configuration with YAML (Python 2.7)
=============================================================

Requires PyYAML -> "easy_install PyYAML"

See the recipes for configuring logging with dicts and YAML
- http://docs.python.org/2.7/howto/logging-cookbook.html
- http://stackoverflow.com/questions/10519392/python2-7-logging-configuration-with-yaml
"""

import logging
import logging.config
import yaml
import StringIO

# Should be a config file in real app

YAML_CONF = """\
%YAML 1.2
---
# Config  for my application
# --------------------------
myapp:
  foo: bar
  bar: [1, 2]

# Config for logging
# ------------------
# See http://docs.python.org/2.7/library/logging.config.html#configuration-dictionary-schema

logging:
  version: 1
  disable_existing_loggers: true

  # Configuring the default (root) logger is highly recommended

  root:
    level: !!python/name:logging.NOTSET
    handlers: [console]

  loggers:

    # Logging from my application

    myapp.lib:
      level: !!python/name:logging.WARN
      handlers: [logfile]
      qualname: myapp.lib
      propagate: false
    myapp.cli:
      level: !!python/name:logging.WARN
      handlers: [console]
      qualname: myapp.cli
      propagate: false

    # Controlling logging of 3rd party libs

    sqlalchemy.engine:
      level: !!python/name:logging.WARN
      handlers: [logfile]
      qualname: sqlalchemy.engine
      propagate: false
    sqlalchemy.pool:
      level: !!python/name:logging.WARN
      handlers: [logfile]
      qualname: sqlalchemy.pool
      propagate: false

  handlers:
    logfile:
      class: logging.FileHandler
      filename: sample.log
      formatter: simpleFormatter
      level: !!python/name:logging.NOTSET
    console:
      class: logging.StreamHandler
      stream: ext://sys.stdout
      formatter: simpleFormatter
      level: !!python/name:logging.NOTSET

  formatters:
    simpleFormatter:
      class: !!python/name:logging.Formatter
      format: '%(name)s %(asctime)s %(levelname)s %(message)s'
      datefmt: '%d/%m/%Y %H:%M:%S'
"""

# Loading config. Of course this is in another file in the real life

global_config = yaml.load(StringIO.StringIO(YAML_CONF))

# Configuring logging with the subset of the dict
#

logging.config.dictConfig(global_config['logging'])

# Using explicitely the root logger always logs to the console

logging.info("This is an info of the root logger")

# The unconfigured loggers are captured by the root logger (-> console)

unconfigured_logger = logging.getLogger('unconfigured')
unconfigured_logger.info("This is an info from an unknown / unconfigured source")

# Logging from myapp.cli

myapp_cli_logger = logging.getLogger('myapp.cli')
myapp_cli_logger.info("This is an info from myapp.cli")  # Not recorded
myapp_cli_logger.warning("This is a warning from myapp.cli")  # -> console

# Logging from myapp.lib

myapp_lib_logger = logging.getLogger('myapp.lib')
myapp_lib_logger.info("This is an info from myapp.lib")  # Not recorded
myapp_lib_logger.warning("This is a warning from myapp.lib")  # -> sample.log

# Controlling logs from 3rd party libs

sqla_logger = logging.getLogger('sqlalchemy.engine')
sqla_logger.info("This is an info from SQLAlchemy")  # Not recorded
sqla_logger.warning("This is a warning from SQLAlchemy")  # -> sample.log

print "Now look at the file 'sample.log'"

great example !

but you repeated twice the same link
http://docs.python.org/2.7/howto/logging-cookbook.html ;)

Thanks for this. I removed the noise.

For future readers: The qualname key does not apply to dictionary-based configuration. It's only relevant to the fileConfig method, which uses the ConfigParser/.ini file configuration method. It doesn't cause a problem in this example because the qualnames are always the same as the dictionary key (which is what's actually used with dictionary-based config), but if you try to use a shorthand name for the dictionary key and then use a real/qualified name in qualname, your configured logger will not be picked up at runtime.

Thank you from japan.

Thank youso much. It was totally helpful from Korea.

What about custom filters?

@Olegt0rr
Please, check my comment at this other gist