Python:日志模块logging的应用

  在Python中，上面以实现的和已经实现的，都可以使用logging模块迅速搞定，且仅仅只须要一个配置文件，两行代码，实现过程以下（仅以输出的磁盘文件为例，命令输出只须要修改配置文件便可，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，其余同样，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，若是使用python本身的，有如下四个级别：

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，很方便的作到了日志级别控制。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。

#!/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，内容以下:
[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.