Python:日誌模塊logging的應用

  在Python中，上面以實現的和已經實現的，都可以使用logging模塊迅速搞定，且僅僅只須要一個配置文件，兩行代碼，實現過程以下（僅以輸出的磁盤文件爲例，命令輸出只須要修改配置文件便可，具體可查API手冊）：

1. 定義配置文件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)

注意前三個[ ]中的keys，這個在後面各[ ]中定義定義，section的取名格式如looger_自定義名稱， handler_自定義名稱，我偷懶直接使用了標準名稱，其餘同樣，最後一個要注意的就是format,即日誌文件中內容的格式，具體見後面附一。level參數是日誌級別，可擴展，若是使用python本身的，有如下四個級別：

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

例如配置文件中level定義爲WARN,則INFO, DEBUG,NOTSET三個級別的日誌點則不會輸出，很方便的作到了日誌級別控制。args定義了日誌方件名，寫方式，最大大小，保存最多個數等屬性。

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import logging
import logging.config

#日誌初始化
LOG_FILENAME = 'logging.conf'
logging.config.fileConfig(LOG_FILENAME)
logger = logging.getLogger("simple_log_example")

#測試代碼
logger.debug("debug message")
logger.info("info message")
logger.warn("warn message")
logger.error("error message")
logger.critical("critical message")

運行後，查看日誌文件，內容以下:
[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

如將日誌級別設置爲WARN，再次運行，查看日誌：
[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參數格式說明：

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.