python的logging模块

1.简单的将日志打印到屏幕

import logging

logging.debug('This is debug message')
logging.info('This is info message')
logging.warning('This is warning message')
 
屏幕上打印: 
WARNING:root:Thisis warning message

 默认情况下，logging将日志打印到屏幕，日志级别为WARNING；

 日志级别大小关系为：CRITICAL > ERROR > WARNING > INFO > DEBUG > NOTSET，当然也可以自己定义日志级别。

2.通过logging.basicConfig函数对日志的输出格式及方式做相关配置

import logging

logging.basicConfig(level=logging.DEBUG,
                format='%(asctime)s %(filename)s[line:%(lineno)d] %(levelname)s %(message)s',
                datefmt='%a, %d %b %Y %H:%M:%S',
                filename='myapp.log',
                filemode='w')
    
logging.debug('This is debug message')
logging.info('This is info message')
logging.warning('This is warning message')
 
./myapp.log文件中内容为:
Sun, 24 May 2009 21:48:54 demo2.py[line:11] DEBUG This is debug message
Sun, 24 May 2009 21:48:54 demo2.py[line:12] INFO This is info message
Sun, 24 May 2009 21:48:54 demo2.py[line:13] WARNING This is warning message

logging.basicConfig函数各参数:
filename: 指定日志文件名
filemode: 和file函数意义相同，指定日志文件的打开模式，'w'或'a'
format: 指定输出的格式和内容，format可以输出很多有用信息，如上例所示:
%(levelno)s: 打印日志级别的数值
%(levelname)s: 打印日志级别名称
%(pathname)s: 打印当前执行程序的路径，其实就是sys.argv[0]
%(filename)s: 打印当前执行程序名
%(funcName)s: 打印日志的当前函数
%(lineno)d: 打印日志的当前行号
%(asctime)s: 打印日志的时间
%(thread)d: 打印线程ID
%(threadName)s: 打印线程名称
%(process)d: 打印进程ID
%(message)s: 打印日志信息
datefmt: 指定时间格式，同time.strftime()
level: 设置日志级别，默认为logging.WARNING
stream: 指定将日志的输出流，可以指定输出到sys.stderr,sys.stdout或者文件，默认输出到sys.stderr，当stream和filename同时指定时，stream被忽略

import os
import logging
import logging.handlers
 
def init_log(log_path, level=logging.INFO, when="D", backup=7,
             format="%(levelname)s: %(asctime)s: %(filename)s:%(lineno)d * %(thread)d %(message)s",
             datefmt="%m-%d %H:%M:%S"):
    """
    init_log - initialize log module
     
    Args:
      log_path      - Log file path prefix.
                      Log data will go to two files: log_path.log and log_path.log.wf
                      Any non-exist parent directories will be created automatically
      level         - msg above the level will be displayed
                      DEBUG < INFO < WARNING < ERROR < CRITICAL
                      the default value is logging.INFO
      when          - how to split the log file by time interval
                      'S' : Seconds
                      'M' : Minutes
                      'H' : Hours
                      'D' : Days
                      'W' : Week day
                      default value: 'D'
      format        - format of the log
                      default format:
                      %(levelname)s: %(asctime)s: %(filename)s:%(lineno)d * %(thread)d %(message)s
                      INFO: 12-09 18:02:42: log.py:40 * 139814749787872 HELLO WORLD
      backup        - how many backup file to keep
                      default value: 7
 
    Raises:
        OSError: fail to create log directories
        IOError: fail to open log file
    """
    formatter = logging.Formatter(format, datefmt)
    logger = logging.getLogger()
    logger.setLevel(level)
 
    dir = os.path.dirname(log_path)
    if not os.path.isdir(dir):
        os.makedirs(dir)
 
    handler = logging.handlers.TimedRotatingFileHandler(log_path + ".log",
                                                        when=when,
                                                        backupCount=backup)
    handler.setLevel(level)
    handler.setFormatter(formatter)
    logger.addHandler(handler)
 
    handler = logging.handlers.TimedRotatingFileHandler(log_path + ".log.wf",
                                                        when=when,
                                                        backupCount=backup)
    handler.setLevel(logging.WARNING)
    handler.setFormatter(formatter)
    logger.addHandler(handler)