Python:日志模块logging的应用



  通常，在商用软件中均会有完整的日志机制，之前使用C语言实现过一个《简单的分级别写日志程序》，具有以下功能和不足：

在Python中，上面以实现的和已经实现的，均可以使用logging模块迅速搞定，且仅仅只需要一个配置文件，两行代码，实现过程如下（仅以输出的磁盘文件为例，命令输出只需要修改配置文件即可，具体可查API手册）：

1. 定义配置文件logging.conf：

[loggers]  keys=root,applog  [handlers]  keys=rotateFileHandler  [formatters]  keys=applog_format    [formatter_applog_format]  format=[%(asctime)s - %(name)s]%(levelname)s:  %(message)s - %(filename)s:%(lineno)d    [logger_root]  level=NOTSET  handlers=rotateFileHandler    [logger_applog]  level=NOTSET  handlers=rotateFileHandler  qualname=simple_example    [handler_rotateFileHandler]  class=handlers.RotatingFileHandler  level=NOTSET  formatter=applog_format  args=('log_1.log', 'a', 10000, 9) 

注意前三个[ ]中的keys，这个在后面各[ ]中定义定义，section的取名格式如looger_自定义名称， handler_自定义名称，我偷懒直接使用了标准名称，其他一样，最后一个要注意的就是format,即日志文件中内容的格式，具体见后面附一。level参数是日志级别，可扩展，如果使用python自己的，有以下四个级别：

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

例如配置文件中level定义为WARN,则INFO, DEBUG,NOTSET三个级别的日志点则不会输出，很方便的做到了日志级别控制。

args定义了日志方件名，写方式，最大大小，保存最多个数等属性。

2.编码，测试

#!/usr/bin/env python  # -*- coding: utf-8 -*-    import logging  import logging.config    #日志初始化  LOG_FILENAME = 'logging.conf'  logging.config.fileConfig(LOG_FILENAME)  logger = logging.getLogger("simple_log_example")    #测试代码  logger.debug("debug message")  logger.info("info message")  logger.warn("warn message")  logger.error("error message")  logger.critical("critical message")  

运行后，查看日志文件，内容如下:

[2012-02-11 14:47:05,483 - simple_log_example]DEBUG:  debug message - test_log.py:48  [2012-02-11 14:47:05,483 - simple_log_example]INFO:  info message - test_log.py:49  [2012-02-11 14:47:05,483 - simple_log_example]WARNING:  warn message - test_log.py:50  [2012-02-11 14:47:05,483 - simple_log_example]ERROR:  error message - test_log.py:51  [2012-02-11 14:47:05,483 - simple_log_example]CRITICAL:  critical message - test_log.py:52  

如将日志级别设置为WARN，再次运行，查看日志：

[2012-02-11 14:54:20,046 - simple_log_example]WARNING:  warn message - test_log.py:50  [2012-02-11 14:54:20,092 - simple_log_example]ERROR:  error message - test_log.py:51  [2012-02-11 14:54:20,092 - simple_log_example]CRITICAL:  critical message - test_log.py:52  

附一：format参数格式说明：

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.  

利用课余时间，编程赚点小钱