(轉載)
原文:http://www.cnblogs.com/dahu-daqing/p/7040764.html
1 logging模塊簡介
logging模塊是Python內置的標準模塊,主要用於輸出運行日誌,可以設置輸出日誌的等級、日誌保存路徑、日誌文件回滾等;相比print,具備如下優點:
- 可以通過設置不同的日誌等級,在release版本中只輸出重要信息,而不必顯示大量的調試信息;
- print將所有信息都輸出到標準輸出中,嚴重影響開發者從標準輸出中查看其它數據;logging則可以由開發者決定將信息輸出到什麼地方,以及怎麼輸出;
2 logging模塊使用
2.1 基本使用
配置logging基本的設置,然後在控制檯輸出日誌,
import logging logging.basicConfig(level = logging.INFO,format = '%(asctime)s - %(name)s - %(levelname)s - %(message)s') logger = logging.getLogger(__name__) logger.info("Start print log") logger.debug("Do something") logger.warning("Something maybe fail.") logger.info("Finish")
運行時,控制檯輸出,
2016-10-09 19:11:19,434 - __main__ - INFO - Start print log
2016-10-09 19:11:19,434 - __main__ - WARNING - Something maybe fail.
2016-10-09 19:11:19,434 - __main__ - INFO - Finish
logging中可以選擇很多消息級別,如debug、info、warning、error以及critical。通過賦予logger或者handler不同的級別,開發者就可以只輸出錯誤信息到特定的記錄文件,或者在調試時只記錄調試信息。
例如,我們將logger的級別改爲DEBUG,再觀察一下輸出結果,
logging.basicConfig(level = logging.DEBUG,format = '%(asctime)s - %(name)s - %(levelname)s - %(message)s')
控制檯輸出,可以發現,輸出了debug的信息。
2016-10-09 19:12:08,289 - __main__ - INFO - Start print log
2016-10-09 19:12:08,289 - __main__ - DEBUG - Do something
2016-10-09 19:12:08,289 - __main__ - WARNING - Something maybe fail.
2016-10-09 19:12:08,289 - __main__ - INFO - Finish
logging.basicConfig函數各參數:
filename:指定日誌文件名;
filemode:和file函數意義相同,指定日誌文件的打開模式,'w'或者'a';
format:指定輸出的格式和內容,format可以輸出很多有用的信息,
參數:作用
%(levelno)s:打印日誌級別的數值
%(levelname)s:打印日誌級別的名稱
%(pathname)s:打印當前執行程序的路徑,其實就是sys.argv[0]
%(filename)s:打印當前執行程序名
%(funcName)s:打印日誌的當前函數
%(lineno)d:打印日誌的當前行號
%(asctime)s:打印日誌的時間
%(thread)d:打印線程ID
%(threadName)s:打印線程名稱
%(process)d:打印進程ID
%(message)s:打印日誌信息
datefmt:指定時間格式,同time.strftime();
level:設置日誌級別,默認爲logging.WARNNING;
stream:指定將日誌的輸出流,可以指定輸出到sys.stderr,sys.stdout或者文件,默認輸出到sys.stderr,當stream和filename同時指定時,stream被忽略;
2.2 將日誌寫入到文件
2.2.1 將日誌寫入到文件
設置logging,創建一個FileHandler,並對輸出消息的格式進行設置,將其添加到logger,然後將日誌寫入到指定的文件中,
import logging logger = logging.getLogger(__name__) logger.setLevel(level = logging.INFO) handler = logging.FileHandler("log.txt") handler.setLevel(logging.INFO) formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') handler.setFormatter(formatter) logger.addHandler(handler) logger.info("Start print log") logger.debug("Do something") logger.warning("Something maybe fail.") logger.info("Finish")
log.txt中日誌數據爲,
2016-10-09 19:01:13,263 - __main__ - INFO - Start print log
2016-10-09 19:01:13,263 - __main__ - WARNING - Something maybe fail.
2016-10-09 19:01:13,263 - __main__ - INFO - Finish
2.2.2 將日誌同時輸出到屏幕和日誌文件
logger中添加StreamHandler,可以將日誌輸出到屏幕上,
import logging logger = logging.getLogger(__name__) logger.setLevel(level = logging.INFO) handler = logging.FileHandler("log.txt") handler.setLevel(logging.INFO) formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') handler.setFormatter(formatter) console = logging.StreamHandler() console.setLevel(logging.INFO) logger.addHandler(handler) logger.addHandler(console) logger.info("Start print log") logger.debug("Do something") logger.warning("Something maybe fail.") logger.info("Finish")
可以在log.txt文件和控制檯中看到,
2016-10-09 19:20:46,553 - __main__ - INFO - Start print log
2016-10-09 19:20:46,553 - __main__ - WARNING - Something maybe fail.
2016-10-09 19:20:46,553 - __main__ - INFO - Finish
可以發現,logging有一個日誌處理的主對象,其他處理方式都是通過addHandler添加進去,logging中包含的handler主要有如下幾種,
handler名稱:位置;作用
StreamHandler:logging.StreamHandler;日誌輸出到流,可以是sys.stderr,sys.stdout或者文件
FileHandler:logging.FileHandler;日誌輸出到文件
BaseRotatingHandler:logging.handlers.BaseRotatingHandler;基本的日誌回滾方式
RotatingHandler:logging.handlers.RotatingHandler;日誌回滾方式,支持日誌文件最大數量和日誌文件回滾
TimeRotatingHandler:logging.handlers.TimeRotatingHandler;日誌回滾方式,在一定時間區域內回滾日誌文件
SocketHandler:logging.handlers.SocketHandler;遠程輸出日誌到TCP/IP sockets
DatagramHandler:logging.handlers.DatagramHandler;遠程輸出日誌到UDP sockets
SMTPHandler:logging.handlers.SMTPHandler;遠程輸出日誌到郵件地址
SysLogHandler:logging.handlers.SysLogHandler;日誌輸出到syslog
NTEventLogHandler:logging.handlers.NTEventLogHandler;遠程輸出日誌到Windows NT/2000/XP的事件日誌
MemoryHandler:logging.handlers.MemoryHandler;日誌輸出到內存中的指定buffer
HTTPHandler:logging.handlers.HTTPHandler;通過"GET"或者"POST"遠程輸出到HTTP服務器
2.2.3 日誌回滾
使用RotatingFileHandler,可以實現日誌回滾,
import logging from logging.handlers import RotatingFileHandler logger = logging.getLogger(__name__) logger.setLevel(level = logging.INFO) #定義一個RotatingFileHandler,最多備份3個日誌文件,每個日誌文件最大1K rHandler = RotatingFileHandler("log.txt",maxBytes = 1*1024,backupCount = 3) rHandler.setLevel(logging.INFO) formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') rHandler.setFormatter(formatter) console = logging.StreamHandler() console.setLevel(logging.INFO) console.setFormatter(formatter) logger.addHandler(rHandler) logger.addHandler(console) logger.info("Start print log") logger.debug("Do something") logger.warning("Something maybe fail.") logger.info("Finish")
可以在工程目錄中看到,備份的日誌文件,
2016/10/09 19:36 732 log.txt
2016/10/09 19:36 967 log.txt.1
2016/10/09 19:36 985 log.txt.2
2016/10/09 19:36 976 log.txt.3
2.3 設置消息的等級
可以設置不同的日誌等級,用於控制日誌的輸出,
日誌等級:使用範圍
FATAL:致命錯誤
CRITICAL:特別糟糕的事情,如內存耗盡、磁盤空間爲空,一般很少使用
ERROR:發生錯誤時,如IO操作失敗或者連接問題
WARNING:發生很重要的事件,但是並不是錯誤時,如用戶登錄密碼錯誤
INFO:處理請求或者狀態變化等日常事務
DEBUG:調試過程中使用DEBUG等級,如算法中每個循環的中間狀態
2.4 捕獲traceback
Python中的traceback模塊被用於跟蹤異常返回信息,可以在logging中記錄下traceback,
代碼,
import logging logger = logging.getLogger(__name__) logger.setLevel(level = logging.INFO) handler = logging.FileHandler("log.txt") handler.setLevel(logging.INFO) formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') handler.setFormatter(formatter) console = logging.StreamHandler() console.setLevel(logging.INFO) logger.addHandler(handler) logger.addHandler(console) logger.info("Start print log") logger.debug("Do something") logger.warning("Something maybe fail.") try: open("sklearn.txt","rb") except (SystemExit,KeyboardInterrupt): raise except Exception: logger.error("Faild to open sklearn.txt from logger.error",exc_info = True) logger.info("Finish")
控制檯和日誌文件log.txt中輸出,
Start print log
Something maybe fail.
Faild to open sklearn.txt from logger.error
Traceback (most recent call last):
File "G:\zhb7627\Code\Eclipse WorkSpace\PythonTest\test.py", line 23, in <module>
open("sklearn.txt","rb")
IOError: [Errno 2] No such file or directory: 'sklearn.txt'
Finish
也可以使用logger.exception(msg,_args),它等價於logger.error(msg,exc_info = True,_args),
將
logger.error("Faild to open sklearn.txt from logger.error",exc_info = True)
替換爲,
logger.exception("Failed to open sklearn.txt from logger.exception")
控制檯和日誌文件log.txt中輸出,
Start print log
Something maybe fail.
Failed to open sklearn.txt from logger.exception
Traceback (most recent call last):
File "G:\zhb7627\Code\Eclipse WorkSpace\PythonTest\test.py", line 23, in <module>
open("sklearn.txt","rb")
IOError: [Errno 2] No such file or directory: 'sklearn.txt'
Finish
2.5 多模塊使用logging
主模塊mainModule.py,
import logging import subModule logger = logging.getLogger("mainModule") logger.setLevel(level = logging.INFO) handler = logging.FileHandler("log.txt") handler.setLevel(logging.INFO) formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') handler.setFormatter(formatter) console = logging.StreamHandler() console.setLevel(logging.INFO) console.setFormatter(formatter) logger.addHandler(handler) logger.addHandler(console) logger.info("creating an instance of subModule.subModuleClass") a = subModule.SubModuleClass() logger.info("calling subModule.subModuleClass.doSomething") a.doSomething() logger.info("done with subModule.subModuleClass.doSomething") logger.info("calling subModule.some_function") subModule.som_function() logger.info("done with subModule.some_function")
子模塊subModule.py,
import logging module_logger = logging.getLogger("mainModule.sub") class SubModuleClass(object): def __init__(self): self.logger = logging.getLogger("mainModule.sub.module") self.logger.info("creating an instance in SubModuleClass") def doSomething(self): self.logger.info("do something in SubModule") a = [] a.append(1) self.logger.debug("list a = " + str(a)) self.logger.info("finish something in SubModuleClass") def som_function(): module_logger.info("call function some_function")
執行之後,在控制和日誌文件log.txt中輸出,
2016-10-09 20:25:42,276 - mainModule - INFO - creating an instance of subModule.subModuleClass
2016-10-09 20:25:42,279 - mainModule.sub.module - INFO - creating an instance in SubModuleClass
2016-10-09 20:25:42,279 - mainModule - INFO - calling subModule.subModuleClass.doSomething
2016-10-09 20:25:42,279 - mainModule.sub.module - INFO - do something in SubModule
2016-10-09 20:25:42,279 - mainModule.sub.module - INFO - finish something in SubModuleClass
2016-10-09 20:25:42,279 - mainModule - INFO - done with subModule.subModuleClass.doSomething
2016-10-09 20:25:42,279 - mainModule - INFO - calling subModule.some_function
2016-10-09 20:25:42,279 - mainModule.sub - INFO - call function some_function
2016-10-09 20:25:42,279 - mainModule - INFO - done with subModule.some_function
首先在主模塊定義了logger'mainModule',並對它進行了配置,就可以在解釋器進程裏面的其他地方通過getLogger('mainModule')得到的對象都是一樣的,不需要重新配置,可以直接使用。定義的該logger的子logger,都可以共享父logger的定義和配置,所謂的父子logger是通過命名來識別,任意以'mainModule'開頭的logger都是它的子logger,例如'mainModule.sub'。
實際開發一個application,首先可以通過logging配置文件編寫好這個application所對應的配置,可以生成一個根logger,如'PythonAPP',然後在主函數中通過fileConfig加載logging配置,接着在application的其他地方、不同的模塊中,可以使用根logger的子logger,如'PythonAPP.Core','PythonAPP.Web'來進行log,而不需要反覆的定義和配置各個模塊的logger。
3 通過JSON或者YAML文件配置logging模塊
儘管可以在Python代碼中配置logging,但是這樣並不夠靈活,最好的方法是使用一個配置文件來配置。在Python 2.7及以後的版本中,可以從字典中加載logging配置,也就意味着可以通過JSON或者YAML文件加載日誌的配置。
3.1 通過JSON文件配置
JSON配置文件,
{
"version":1,
"disable_existing_loggers":false,
"formatters":{
"simple":{
"format":"%(asctime)s - %(name)s - %(levelname)s - %(message)s"
}
},
"handlers":{
"console":{
"class":"logging.StreamHandler",
"level":"DEBUG",
"formatter":"simple",
"stream":"ext://sys.stdout"
},
"info_file_handler":{
"class":"logging.handlers.RotatingFileHandler",
"level":"INFO",
"formatter":"simple",
"filename":"info.log",
"maxBytes":"10485760",
"backupCount":20,
"encoding":"utf8"
},
"error_file_handler":{
"class":"logging.handlers.RotatingFileHandler",
"level":"ERROR",
"formatter":"simple",
"filename":"errors.log",
"maxBytes":10485760,
"backupCount":20,
"encoding":"utf8"
}
},
"loggers":{
"my_module":{
"level":"ERROR",
"handlers":["info_file_handler"],
"propagate":"no"
}
},
"root":{
"level":"INFO",
"handlers":["console","info_file_handler","error_file_handler"]
}
}
通過JSON加載配置文件,然後通過logging.dictConfig配置logging,
import json import logging.config import os def setup_logging(default_path = "logging.json",default_level = logging.INFO,env_key = "LOG_CFG"): path = default_path value = os.getenv(env_key,None) if value: path = value if os.path.exists(path): with open(path,"r") as f: config = json.load(f) logging.config.dictConfig(config) else: logging.basicConfig(level = default_level) def func(): logging.info("start func") logging.info("exec func") logging.info("end func") if __name__ == "__main__": setup_logging(default_path = "logging.json") func()
3.2 通過YAML文件配置
通過YAML文件進行配置,比JSON看起來更加簡介明瞭,
version: 1
disable_existing_loggers: False
formatters:
simple:
format: "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
handlers:
console:
class: logging.StreamHandler
level: DEBUG
formatter: simple
stream: ext://sys.stdout
info_file_handler:
class: logging.handlers.RotatingFileHandler
level: INFO
formatter: simple
filename: info.log
maxBytes: 10485760
backupCount: 20
encoding: utf8
error_file_handler:
class: logging.handlers.RotatingFileHandler
level: ERROR
formatter: simple
filename: errors.log
maxBytes: 10485760
backupCount: 20
encoding: utf8
loggers:
my_module:
level: ERROR
handlers: [info_file_handler]
propagate: no
root:
level: INFO
handlers: [console,info_file_handler,error_file_handler]
通過YAML加載配置文件,然後通過logging.dictConfig配置logging,
import yaml import logging.config import os def setup_logging(default_path = "logging.yaml",default_level = logging.INFO,env_key = "LOG_CFG"): path = default_path value = os.getenv(env_key,None) if value: path = value if os.path.exists(path): with open(path,"r") as f: config = yaml.load(f) logging.config.dictConfig(config) else: logging.basicConfig(level = default_level) def func(): logging.info("start func") logging.info("exec func") logging.info("end func") if __name__ == "__main__": setup_logging(default_path = "logging.yaml") func()