python logging system

官方教程：https://docs.python.org/2/library/logging.html 

1.  用法1

import logging
import logging.handlers

LOG_FILE = 'tst.log'

handler = logging.handlers.RotatingFileHandler(LOG_FILE, maxBytes = 1024*1024, backupCount = 5) # 实例化handler 
fmt = '%(asctime)s - %(filename)s:%(lineno)s - %(name)s - %(message)s'

formatter = logging.Formatter(fmt)   # 实例化formatter
handler.setFormatter(formatter)      # 为handler添加formatter

logger = logging.getLogger('tst')    # 获取名为tst的logger
logger.addHandler(handler)           # 为logger添加handler
logger.setLevel(logging.DEBUG)

logger.info('first info message')
logger.debug('first debug message')

formatter

　　采用的是%(<dict key>)s的形式，就是字典的关键字替换。提供的关键字包括：

Format	Description
%(name)s	Name of the logger (logging channel).
%(levelno)s	Numeric logging level for the message (DEBUG, INFO, WARNING, ERROR, CRITICAL).
%(levelname)s	Text logging level for the message ('DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL').
%(pathname)s	Full pathname of the source file where the logging call was issued (if available).
%(filename)s	Filename portion of pathname.
%(module)s	Module (name portion of filename).
%(funcName)s	Name of function containing the logging call.
%(lineno)d	Source line number where the logging call was issued (if available).
%(created)f	Time when the LogRecord was created (as returned by time.time()).
%(relativeCreated)d	Time in milliseconds when the LogRecord was created, relative to the time the logging module was loaded.
%(asctime)s	Human-readable time when the LogRecord was created. By default this is of the form “2003-07-08 16:49:45,896” (the numbers after the comma are millisecond portion of the time).
%(msecs)d	Millisecond portion of the time when the LogRecord was created.
%(thread)d	Thread ID (if available).
%(threadName)s	Thread name (if available).
%(process)d	Process ID (if available).
%(message)s	The logged message, computed as msg % args.

 level

The numeric values of logging levels are given in the following table. These are primarily of interest if you want to define your own levels, and need them to have specific values relative to the predefined levels. If you define a level with the same numeric value, it overwrites the predefined value; the predefined name is lost.

Level	Numeric value
CRITICAL	50
ERROR	40
WARNING	30
INFO	20
DEBUG	10
NOTSET	0

 如果指定level 为INFO, 则小于它的所有message都不会打印出来。

2. 用法2

　　采用配置文件的方式去配置logging system， 这种方法简单方便，可以在多模块间调用而不需要传入logger对象。

现在我准备一个配置文件logging.conf如下

[loggers]
keys=root,uploader,msgChanger   #

[handlers]
keys=consoleHandler,uploaderHandler,msgChangerHandler

[formatters]
keys=fmt

[logger_root]
level=INFO
handlers=consoleHandler
qualname=root

[logger_uploader]
level=INFO
qualname=uploader
handlers=uploaderHandler

[logger_msgChanger]
level=INFO
qualname=msgChanger
handlers=msgChangerHandler

[handler_consoleHandler]
class=StreamHandler
level=INFO
formatter=fmt
args=(sys.stdout,)

[handler_uploaderHandler]
class=logging.handlers.RotatingFileHandler
level=INFO
formatter=fmt
args=('log/uploader.log','w',1024*1024*1024,5,)

[handler_msgChangerHandler]
class=logging.handlers.RotatingFileHandler
level=INFO
formatter=fmt
args=('log/msg_changer.log','w',1024*1024*1024,5,)

[formatter_fmt]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=

 called in code:

'''init log module'''
    logging.config.fileConfig('config/logging.conf')   # parse config file as above   
    msgChanger_logger = logging.getLogger('msgChanger.main') # get a logger instance, msgChanger must be included 
　　msgChanger_logger.info('test log system in main.')

 可以在任何module下写入上述代码调用logger, 只需要传入一个名字就好了，名字必须在config文件里配置了的，否则实例失败。