Python 日志输出,模块logging的使用

在实习之前,日志我基本上都是用输出printf,实习期间发现在做项目时,这种输出日志的方式已经不能满足需求了.

于是在网上查了下,发现python  logging模块真的非常好用,在这里简单的记录下.

举个例子:

 #coding:utf-8
 import logging
 import logging.handlers
 
 log_file = 'test.log'
 
 handler = logging.handlers.RotatingFileHandler(log_file, maxBytes = 1024*1024, backupCount = 5)
 
 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('test')    # 获取名为test的logger
 logger.addHandler(handler)           # 为logger添加handler
 logger.setLevel(logging.INFO)       # 设置存入文件的log等级
 
 logger.info('first info message')  #能够输出到指定的log文件
 logger.debug('first debug message') #log等级小于指定的的等级,不能输出到指的log文件

执行代码后,查看test.log文件(这个文件会自动生成,之后会追加日志):

(crawler_env) [liangping@localhost ~]$ cat test.log 
2017-09-28 17:44:04,188 - log_test.py:18 - test - first info message

至于formatter的配置，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.