logging example
| Level | When it’s used | Numeric value |
|---|---|---|
| DEBUG | Detailed information, typically of interest only when diagnosing problems. | 10 |
| INFO | Confirmation that things are working as expected. | 20 |
| WARNING | An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected. | 30 |
| ERROR | Due to a more serious problem, the software has not been able to perform some function. | 40 |
| CRITICAL | A serious error, indicating that the program itself may be unable to continue running. | 50 |
The default level is WARNING, which means that only events of this level and above will be tracked, unless the logging package is configured to do otherwise.
logging to a file
if you run the above script several times, the messages from successive runs are appended to the file example.log. If you want each run to start afresh, not remembering the messages from earlier runs, you can specify the filemode argument, by changing the call in the above example to:
logging.basicConfig(filename='example.log', filemode='w', level=logging.DEBUG)
Configuring Logging
Programmers can configure logging in three ways:
Creating loggers, handlers, and formatters explicitly using Python code that calls the configuration methods listed above.
Creating a logging config file and reading it using the fileConfig() function.
Creating a dictionary of configuration information and passing it to the dictConfig() function.
For the reference documentation on the last two options, see Configuration functions. The following example configures a very simple logger, a console handler, and a simple formatter using Python code:
import logging
# create logger
logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)
# create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)
# create formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
# add formatter to ch
ch.setFormatter(formatter)
# add ch to logger
logger.addHandler(ch)
# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')
output:
2018-05-28 19:23:50,651 - simple_example - DEBUG - debug message
2018-05-28 19:23:50,651 - simple_example - INFO - info message
2018-05-28 19:23:50,651 - simple_example - WARNING - warn message
2018-05-28 19:23:50,651 - simple_example - ERROR - error message
2018-05-28 19:23:50,651 - simple_example - CRITICAL - critical message
The following Python module creates a logger, handler, and formatter nearly identical to those in the example listed above, with the only difference being the names of the objects:
import logging
import logging.config
logging.config.fileConfig('logging.conf')
# create logger
logger = logging.getLogger('simpleExample')
# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')
Here is the logging.conf file:
[loggers]
keys=root,simpleExample
[handlers]
keys=consoleHandler
[formatters]
keys=simpleFormatter
[logger_root]
level=DEBUG
handlers=consoleHandler
[logger_simpleExample]
level=DEBUG
handlers=consoleHandler
qualname=simpleExample
propagate=0
[handler_consoleHandler]
class=StreamHandler
level=DEBUG
formatter=simpleFormatter
args=(sys.stdout,)
[formatter_simpleFormatter]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=
The output is nearly identical to that of the non-config-file-based example:
$ python simple_logging_config.py
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message
Example
例1
logging模块最简单的用法，是直接使用basicConfig方法来对logging进行配置
import logging
# 设置默认的level为DEBUG
# 设置log的格式
logging.basicConfig(
level=logging.DEBUG,
format="[%(asctime)s] %(name)s:%(levelname)s: %(message)s"
)
例2
import os
import logging
import sys
def test_log_level():
# set default logging configuration
logger = logging.getLogger() # initialize logging class
logger.setLevel(logging.DEBUG) # default log level
format = logging.Formatter("%(asctime)s - %(message)s") # output format
sh = logging.StreamHandler() # output to standard output
sh.setFormatter(format)
logger.addHandler(sh)
# use logging to generate log ouput
logger.info("this is info")
logger.debug("this is debug")
logger.warning("this is warning")
logging.error("this is error")
logger.critical("this is critical")
test_log_level()
[Running] python "d:\OneDrive\02-coding\test\test-logging.py"
[2018-03-11 20:08:37,533] root:DEBUG: hello
[2018-03-11 20:08:37,533] root:INFO: world111
[2018-03-11 20:08:37,533] root:WARNING: world
[2018-03-11 20:08:37,534] root:ERROR: world
[2018-03-11 20:08:37,534] root:CRITICAL: world