1. logging介紹
Python的logging模塊提供了通用的日誌系統,可以方便第三方模塊或者是應用使用。這個模塊提供不同的日誌級別,並可以採用不同的方式記錄日誌,比如文件,HTTP GET/POST,SMTP,Socket等,甚至可以自己實現具體的日誌記錄方式。
logging模塊與log4j的機制是一樣的,只是具體的實現細節不同。模塊提供logger,handler,filter,formatter。
logger:提供日誌接口,供應用代碼使用。logger最長用的操作有兩類:配置和發送日誌消息。可以通過logging.getLogger(name)獲取logger對象,如果不指定name則返回root對象,多次使用相同的name調用getLogger方法返回同一個logger對象。
handler:將日誌記錄(log record)發送到合適的目的地(destination),比如文件,socket等。一個logger對象可以通過addHandler方法添加0到多個handler,每個handler又可以定義不同日誌級別,以實現日誌分級過濾顯示。
filter:提供一種優雅的方式決定一個日誌記錄是否發送到handler。
formatter:指定日誌記錄輸出的具體格式。formatter的構造方法需要兩個參數:消息的格式字符串和日期字符串,這兩個參數都是可選的。
與log4j類似,logger,handler和日誌消息的調用可以有具體的日誌級別(Level),只有在日誌消息的級別大於logger和handler的級別。
- import logging
- import logging.handlers
- LOG_FILE = 'tst.log'
- handler = logging.handlers.RotatingFileHandler(LOG_FILE, maxBytes = 1024*1024, backupCount = 5) # 實例化handler
- fmt = '%(asctime)s - %(filename)s:%(lineno)s - %(name)s - %(message)s'
- formatter = logging.Formatter(fmt) # 實例化formatter
- handler.setFormatter(formatter) # 爲handler添加formatter
- logger = logging.getLogger('tst') # 獲取名爲tst的logger
- logger.addHandler(handler) # 爲logger添加handler
- logger.setLevel(logging.DEBUG)
- logger.info('first info message')
- logger.debug('first debug message')
2012-03-04 23:21:59,682 - log_test.py:16 - tst - first info message
2012-03-04 23:21:59,682 - log_test.py:17 - tst - first debug message
關於formatter的配置,採用的是%(<dict key>)s的形式,就是字典的關鍵字替換。提供的關鍵字包括: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. |
這個是摘自官網,提供了很多信息。
2. logging的配置
logging的配置可以採用python代碼或是配置文件。python代碼的方式就是在應用的主模塊中,構建handler,handler,formatter等對象。而配置文件的方式是將這些對象的依賴關係分離出來放在文件中。比如前面的例子就類似於python代碼的配置方式。這裏看一下采用配置文件的方式。
- import logging
- import logging.config
- logging.config.fileConfig("logging.conf") # 採用配置文件
- # create logger
- logger = logging.getLogger("simpleExample")
- # "application" code
- logger.debug("debug message")
- logger.info("info message")
- logger.warn("warn message")
- logger.error("error message")
- logger.critical("critical message")
[loggers]
keys=root,simpleExample
[handlers]
keys=consoleHandler
[formatters]
keys=simpleFormatter
[logger_root]
level=DEBUG
handlers=consoleHandler
[logger_simpleExample]
level=DEBUG
handlers=consoleHandler
qualname=simpleExample
propagate=0
[handler_consoleHandler]
class=StreamHandler
level=DEBUG
formatter=simpleFormatter
args=(sys.stdout,)
[formatter_simpleFormatter]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=
在指定handler的配置時,class是具體的handler類的類名,可以是相對logging模塊或是全路徑類名,比如需要RotatingFileHandler,則class的值可以爲:RotatingFileHandler或者logging.handlers.RotatingFileHandler。args就是要傳給這個類的構造方法的參數,就是一個元組,按照構造方法聲明的參數的順序。
輸出:
2012-03-06 00:09:35,713 - simpleExample - DEBUG - debug message
2012-03-06 00:09:35,713 - simpleExample - INFO - info message
2012-03-06 00:09:35,714 - simpleExample - WARNING - warn message
2012-03-06 00:09:35,714 - simpleExample - ERROR - error message
2012-03-06 00:09:35,714 - simpleExample - CRITICAL - critical message
這裏還要明確一點,logger對象是有繼承關係的,比如名爲a.b和a.c的logger都是名爲a的子logger,並且所有的logger對象都繼承於root。如果子對象沒有添加handler等一些配置,會從父對象那繼承。這樣就可以通過這種繼承關係來複用配置。
3. 多模塊使用logging
這裏使用上面配置文件:
[loggers]
keys=root,main
[handlers]
keys=consoleHandler,fileHandler
[formatters]
keys=fmt
[logger_root]
level=DEBUG
handlers=consoleHandler
[logger_main]
level=DEBUG
qualname=main
handlers=fileHandler
[handler_consoleHandler]
class=StreamHandler
level=DEBUG
formatter=fmt
args=(sys.stdout,)
[handler_fileHandler]
class=logging.handlers.RotatingFileHandler
level=DEBUG
formatter=fmt
args=('tst.log','a',20000,5,)
[formatter_fmt]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=
主模塊main.py:
- import logging
- import logging.config
- logging.config.fileConfig('logging.conf')
- root_logger = logging.getLogger('root')
- root_logger.debug('test root logger...')
- logger = logging.getLogger('main')
- logger.info('test main logger')
- logger.info('start import module \'mod\'...')
- import mod
- logger.debug('let\'s test mod.testLogger()')
- mod.testLogger()
- root_logger.info('finish test...')
- import logging
- import submod
- logger = logging.getLogger('main.mod')
- logger.info('logger of mod say something...')
- def testLogger():
- logger.debug('this is mod.testLogger...')
- submod.tst()
- import logging
- logger = logging.getLogger('main.mod.submod')
- logger.info('logger of submod say something...')
- def tst():
- logger.info('this is submod.tst()...')
2012-03-09 18:22:22,793 - root - DEBUG - test root logger...
2012-03-09 18:22:22,793 - main - INFO - test main logger
2012-03-09 18:22:22,809 - main - INFO - start import module 'mod'...
2012-03-09 18:22:22,809 - main.mod.submod - INFO - logger of submod say something...
2012-03-09 18:22:22,809 - main.mod - INFO - logger say something...
2012-03-09 18:22:22,809 - main - DEBUG - let's test mod.testLogger()
2012-03-09 18:22:22,825 - main.mod - DEBUG - this is mod.testLogger...
2012-03-09 18:22:22,825 - main.mod.submod - INFO - this is submod.tst()...
2012-03-09 18:22:22,841 - root - INFO - finish test...
可以看出,和預想的一樣,然後在看一下tst.log,logger配置中的輸出的目的地:2012-03-09 18:22:22,793 - main - INFO - test main logger
2012-03-09 18:22:22,809 - main - INFO - start import module 'mod'...
2012-03-09 18:22:22,809 - main.mod.submod - INFO - logger of submod say something...
2012-03-09 18:22:22,809 - main.mod - INFO - logger say something...
2012-03-09 18:22:22,809 - main - DEBUG - let's test mod.testLogger()
2012-03-09 18:22:22,825 - main.mod - DEBUG - this is mod.testLogger...
2012-03-09 18:22:22,825 - main.mod.submod - INFO - this is submod.tst()...
tst.log中沒有root logger輸出的信息,因爲logging.conf中配置了只有main logger及其子logger使用RotatingFileHandler,而root logger是輸出到標準輸出。