1 根本应用
配置logging根本的设置，而后在控制台输入日志，
import logginglogging.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")运行时，控制台输入，
2016-10-09 19:11:19,434 - __main__ - INFO - Start print log2016-10-09 19:11:19,434 - __main__ - WARNING - Something maybe fail.2016-10-09 19:11:19,434 - __main__ - INFO - Finishlogging中能够抉择很多音讯级别，如debug、info、warning、error以及critical。通过赋予logger或者handler不同的级别，开发者就能够只输入错误信息到特定的记录文件，或者在调试时只记录调试信息。</pre>
例如，咱们将logger的级别改为DEBUG，再察看一下输入后果，</pre>
logging.basicConfig(level = logging.DEBUG,format = '%(asctime)s - %(name)s - %(levelname)s - %(message)s')</pre>
控制台输入，能够发现，输入了debug的信息。
2016-10-09 19:12:08,289 - __main__ - INFO - Start print log2016-10-09 19:12:08,289 - __main__ - DEBUG - Do something2016-10-09 19:12:08,289 - __main__ - WARNING - Something maybe fail.2016-10-09 19:12:08,289 - __main__ - INFO - Finishlogging.basicConfig函数各参数：
filename：指定日志文件名；
filemode：和file函数意义雷同，指定日志文件的关上模式，'w'或者'a'；
format：指定输入的格局和内容，format能够输入很多有用的信息，
参数：作用 %(levelno)s：打印日志级别的数值%(levelname)s：打印日志级别的名称%(pathname)s：打印以后执行程序的门路，其实就是sys.argv[0]%(filename)s：打印以后执行程序名%(funcName)s：打印日志的以后函数%(lineno)d：打印日志的以后行号%(asctime)s：打印日志的工夫%(thread)d：打印线程ID%(threadName)s：打印线程名称%(process)d：打印过程ID%(message)s：打印日志信息datefmt：指定工夫格局，同time.strftime()；</pre>
level：设置日志级别，默认为logging.WARNNING；</pre>
stream：指定将日志的输入流，能够指定输入到sys.stderr，sys.stdout或者文件，默认输入到sys.stderr，当stream和filename同时指定时，stream被疏忽；</pre>
2 将日志写入到文件
2.2.1 将日志写入到文件</pre>
设置logging，创立一个FileHandler，并对输入音讯的格局进行设置，将其增加到logger，而后将日志写入到指定的文件中，
import logginglogger = 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中日志数据为，
2016-10-09 19:01:13,263 - __main__ - INFO - Start print log2016-10-09 19:01:13,263 - __main__ - WARNING - Something maybe fail.2016-10-09 19:01:13,263 - __main__ - INFO - Finish2.2 将日志同时输入到屏幕和日志文件</pre>
logger中增加StreamHandler，能够将日志输入到屏幕上，</pre>
import logginglogger = 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")能够在log.txt文件和控制台中看到，
2016-10-09 19:20:46,553 - __main__ - INFO - Start print log2016-10-09 19:20:46,553 - __main__ - WARNING - Something maybe fail.2016-10-09 19:20:46,553 - __main__ - INFO - Finish能够发现，logging有一个日志解决的主对象，其余解决形式都是通过addHandler增加进去，logging中蕴含的handler次要有如下几种，
handler名称：地位；作用 StreamHandler：logging.StreamHandler；日志输入到流，能够是sys.stderr，sys.stdout或者文件FileHandler：logging.FileHandler；日志输入到文件BaseRotatingHandler：logging.handlers.BaseRotatingHandler；根本的日志回滚形式RotatingHandler：logging.handlers.RotatingHandler；日志回滚形式，反对日志文件最大数量和日志文件回滚TimeRotatingHandler：logging.handlers.TimeRotatingHandler；日志回滚形式，在肯定工夫区域内回滚日志文件SocketHandler：logging.handlers.SocketHandler；近程输入日志到TCP/IPsocketsDatagramHandler：logging.handlers.DatagramHandler；近程输入日志到UDP socketsSMTPHandler：logging.handlers.SMTPHandler；近程输入日志到邮件地址SysLogHandler：logging.handlers.SysLogHandler；日志输入到syslogNTEventLogHandler：logging.handlers.NTEventLogHandler；近程输入日志到Windows NT/2000/XP的事件日志MemoryHandler：logging.handlers.MemoryHandler；日志输入到内存中的指定bufferHTTPHandler：logging.handlers.HTTPHandler；通过"GET"或者"POST"近程输入到HTTP服务器2.3 日志回滚</pre>
应用RotatingFileHandler，能够实现日志回滚，</pre>
import loggingfrom logging.handlers import RotatingFileHandlerlogger = logging.getLogger(__name__)logger.setLevel(level = logging.INFO)#定义一个RotatingFileHandler，最多备份3个日志文件，每个日志文件最大1KrHandler = 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")能够在工程目录中看到，备份的日志文件，
</pre>
2016/10/09 19:36 732 log.txt2016/10/09 19:36 967 log.txt.12016/10/09 19:36 985 log.txt.22016/10/09 19:36 976 log.txt.32.3 设置音讯的等级
能够设置不同的日志等级，用于管制日志的输入，
</pre>
日志等级：应用范畴 FATAL：致命谬误CRITICAL：特地蹩脚的事件，如内存耗尽、磁盘空间为空，个别很少应用ERROR：产生谬误时，如IO操作失败或者连贯问题WARNING：产生很重要的事件，然而并不是谬误时，如用户登录明码谬误INFO：解决申请或者状态变动等日常事务DEBUG：调试过程中应用DEBUG等级，如算法中每个循环的中间状态2.4 捕捉traceback
Python中的traceback模块被用于跟踪异样返回信息，能够在logging中记录下traceback，
代码，
import logginglogger = 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): raiseexcept Exception: logger.error("Faild to open sklearn.txt from logger.error",exc_info = True) logger.info("Finish")控制台和日志文件log.txt中输入，
Start print logSomething maybe fail.Faild to open sklearn.txt from logger.errorTraceback (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也能够应用logger.exception(msg,_args)，它等价于logger.error(msg,exc_info = True,_args)，
将
logger.error("Faild to open sklearn.txt from logger.error",exc_info = True)替换为，
logger.exception("Failed to open sklearn.txt from logger.exception")控制台和日志文件log.txt中输入，
Start print logSomething maybe fail.Failed to open sklearn.txt from logger.exceptionTraceback (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'Finish2.5 多模块应用logging
主模块mainModule.py，
import loggingimport subModulelogger = 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")子模块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")执行之后，在管制和日志文件log.txt中输入，
2016-10-09 20:25:42,276 - mainModule - INFO - creating an instance of subModule.subModuleClass2016-10-09 20:25:42,279 - mainModule.sub.module - INFO - creating an instance in SubModuleClass2016-10-09 20:25:42,279 - mainModule - INFO - calling subModule.subModuleClass.doSomething2016-10-09 20:25:42,279 - mainModule.sub.module - INFO - do something in SubModule2016-10-09 20:25:42,279 - mainModule.sub.module - INFO - finish something in SubModuleClass2016-10-09 20:25:42,279 - mainModule - INFO - done with subModule.subModuleClass.doSomething2016-10-09 20:25:42,279 - mainModule - INFO - calling subModule.some_function2016-10-09 20:25:42,279 - mainModule.sub - INFO - call function some_function2016-10-09 20:25:42,279 - mainModule - INFO - done with subModule.some_function首先在主模块定义了logger'mainModule'，并对它进行了配置，就能够在解释器过程外面的其余中央通过getLogger('mainModule')失去的对象都是一样的，不须要重新配置，能够间接应用。定义的该logger的子logger，都能够共享父logger的定义和配置，所谓的父子logger是通过命名来辨认，任意以'mainModule'结尾的logger都是它的子logger，例如'mainModule.sub'。
理论开发一个application，首先能够通过logging配置文件编写好这个application所对应的配置，能够生成一个根logger，如'PythonAPP'，而后在主函数中通过fileConfig加载logging配置，接着在application的其余中央、不同的模块中，能够应用根logger的子logger，如'PythonAPP.Core'，'PythonAPP.Web'来进行log，而不须要重复的定义和配置各个模块的logger。
3 通过JSON或者YAML文件配置logging模块
只管能够在Python代码中配置logging，然而这样并不够灵便，最好的办法是应用一个配置文件来配置。在Python 2.7及当前的版本中，能够从字典中加载logging配置，也就意味着能够通过JSON或者YAML文件加载日志的配置。
3.1 通过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"] }}通过JSON加载配置文件，而后通过logging.dictConfig配置logging，
import jsonimport logging.configimport 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 通过YAML文件配置
通过YAML文件进行配置，比JSON看起来更加简介明了，
version: 1disable_existing_loggers: Falseformatters: 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: utf8loggers: my_module: level: ERROR handlers: [info_file_handler] propagate: noroot: level: INFO handlers: [console,info_file_handler,error_file_handler]通过YAML加载配置文件，而后通过logging.dictConfig配置logging
import yamlimport logging.configimport 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()文末福利
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