Python 日志打印之logging.config.dictConfig使用总结
#实践环境
WIN 10
Python 3.6.5
#函数说明
logging.config.dictConfig(config)
dictConfig函数位于logging.config模块,该函数通过字典参数config对logging进行配置。3.2版本新增的函数
##参数说明
config 字典类型,包含以下key:
version - 表示版本,该键值为从1开始的整数。该key必选,除此之外,其它key都是可选。
formatters - 日志格式化器,其value值为一个字典,该字典的每个键值对都代表一个Formatter,键值对中,key代表Formatter ID(自定义ID),value为字典,描述如何配置相应的Formatter实例。默认格式为 '%(message)s’
filters - 日志过滤器,其value值为一个字典,该字典的每个键值对都代表一个Filter,键值对中,key代表Filter ID(自定义ID),value为字典,描述如何配置相应的Filter实例。
handlers - 日志处理器,其value值为一个字典,该字典的每个键值对都代表一个Handler,键值对中,key代表Handler ID(自定义ID),value为字典,描述如何配置相应的Handler实例,包含以下配置key:
class (必选). 日志处理器类全称
level (可选). 指定该日志处理器需要处理哪些级别的日志,低于该级别的日志将不被该handler处理。level可以为代表日志级别的整数或者表大写字符串,字符串日志级别和数字日志级别对应关系如下:
CRITICAL = 50
FATAL = CRITICAL
ERROR = 40
WARNING = 30
WARN = WARNING
INFO = 20
DEBUG = 10
NOTSET = 0
下同,不再赘述.
formatter (可选). 指定该日志处理器使用的日志格式化器
filters (可选). 制定该日志处理器使用的日志过滤器
# 上述的class配置项的值,可以使用自定义Handler类,此时,如果自定义Handler类的__init__构造函数还需要其它参数来初始化类实例,可以继续添自定义参数,这些自定义参数被当做关键字参数会自动传递给构造函数。
一个例子:
"handlers": { "console":{ "class":"study.MyLogHandler", "formatter":"brief", "level":"INFO" }, "file": { "class": "logging.handlers.RotatingFileHandler", "formatter": "precise", "filename": "logconfig.log", "maxBytes": 1024, "backupCount": 3 } }
id为console的日志处理器被实例化为一个logging.StreamHandler,使用sys.stout作为基础实例流。id为file的日志处理器则被实例化为具有关键字参数filename ='logconfig.log',maxBytes = 1024,backupCount = 3的 logging.handlers.RotatingFileHandler
loggers - 日志记录器,其value值为一个字典,该字典的每个键值对都代表一个Handler,键值对中,key代表Handler ID,value为字典,描述如何配置相应的Logger实例,包含以下配置key:
level (可选). 指定该日志记录器需要记录哪些级别的日志,低于该级别的日志将不被该logger记录。
propagate (可选). 指定该日志记录器的propagation配置,为布尔值,即True 或 False,用于控制是否向上遍历父辈日志打印器,进而控制当前日志打印器是否共享父辈打印器的日志处理器。True,向上遍历,否则不向上遍历。
filters (可选). 指定该日志记录器使用的日志过滤器
handlers (可选). 制定该日志记录器使用的日志处理器
root - root logger配置。除了不支持propagate配置项以外,该配置的处理过程同处理其它logger的配置一样,配置规则也一样
incremental - 用于判断该config配置是否解释为现有配置的增量配置,还是覆盖原有配置。默认为False,即使用现有fileConfig()API使用的相同语义替换现有配置
disable_existing_loggers - 其value为布尔值,表示是否禁用现有日志记录器(root logger除外),默认值为True,即禁用。如果incremental 键值为True,则忽略该配置项
#代码示例1
study.py
study.py#!/usr/bin/env python# -*- coding:utf-8 -*-'''@CreateTime: 2020/12/29 14:08@Author : shouke'''import loggingimport logging.configLOGGING_CONFIG = { "version": 1, "formatters": { "default": { 'format':'%(asctime)s %(filename)s %(lineno)s %(levelname)s %(message)s', }, "plain": { "format": "%(message)s", }, }, "handlers": { "console": { "class": "logging.StreamHandler", "level": "INFO", "formatter": "default", }, "console_plain": { "class": "logging.StreamHandler", "level":logging.INFO, "formatter": "plain" }, "file":{ "class": "logging.FileHandler", "level":20, "filename": "./log.txt", "formatter": "default", } }, "loggers": { "console_logger": { "handlers": ["console"], "level": "INFO", "propagate": False, }, "console_plain_logger": { "handlers": ["console_plain"], "level": "DEBUG", "propagate": False, }, "file_logger":{ "handlers": ["file"], "level": "INFO", "propagate": False, } }, "disable_existing_loggers": True,}# 运行测试logging.config.dictConfig(LOGGING_CONFIG)logger = logging.getLogger("console_logger")logger.debug('debug message')logger.info('info message')logger.warn('warning message')logger.error('error message')logger.critical('critical message')
运行study.py,结果输出如下
2021-01-09 10:01:59,123 study.py 66 INFO info message
2021-01-09 10:01:59,123 study.py 67 WARNING warning message
2021-01-09 10:01:59,123 study.py 68 ERROR error message
2021-01-09 10:01:59,123 study.py 69 CRITICAL critical message
#代码示例2
基于代码示例1,修改LOGGING_CONFIG及getLogger函数参数
LOGGING_CONFIG = { "version": 1, "formatters": { "default": { 'format':'%(asctime)s %(filename)s %(lineno)s %(levelname)s %(message)s', } }, "handlers": { "console": { "class": "logging.StreamHandler", "level": "INFO", "formatter": "default", } }, "disable_existing_loggers": True, "root": { "handlers": ["console"], "level": "DEBUG" },}# 运行测试logging.config.dictConfig(LOGGING_CONFIG)logger = logging.getLogger("root")logger.debug('debug message')logger.info('info message')logger.warn('warning message')logger.error('error message')logger.critical('critical message')
运行study.py,结果输出如下
2021-01-09 10:33:03,456 study.py 38 INFO info message
2021-01-09 10:33:03,456 study.py 39 WARNING warning message
2021-01-09 10:33:03,456 study.py 40 ERROR error message
2021-01-09 10:33:03,456 study.py 41 CRITICAL critical message
# 源码的角度分析propagate配置项
Logger类,位于logging/__init__.py
class Logger(Filterer): #...略 def debug(self, msg, *args, **kwargs): """ Log 'msg % args' with severity 'DEBUG'. To pass exception information, use the keyword argument exc_info with a true value, e.g. logger.debug("Houston, we have a %s", "thorny problem", exc_info=1) """ if self.isEnabledFor(DEBUG): self._log(DEBUG, msg, args, **kwargs) def info(self, msg, *args, **kwargs): """ Log 'msg % args' with severity 'INFO'. To pass exception information, use the keyword argument exc_info with a true value, e.g. logger.info("Houston, we have a %s", "interesting problem", exc_info=1) """ if self.isEnabledFor(INFO): self._log(INFO, msg, args, **kwargs) #...略 def _log(self, level, msg, args, exc_info=None, extra=None, stack_info=False): """ Low-level logging routine which creates a LogRecord and then calls all the handlers of this logger to handle the record. """ sinfo = None if _srcfile: #IronPython doesn't track Python frames, so findCaller raises an #exception on some versions of IronPython. We trap it here so that #IronPython can use logging. try: fn, lno, func, sinfo = self.findCaller(stack_info) except ValueError: # pragma: no cover fn, lno, func = "(unknown file)", 0, "(unknown function)" else: # pragma: no cover fn, lno, func = "(unknown file)", 0, "(unknown function)" if exc_info: if isinstance(exc_info, BaseException): exc_info = (type(exc_info), exc_info, exc_info.__traceback__) elif not isinstance(exc_info, tuple): exc_info = sys.exc_info() record = self.makeRecord(self.name, level, fn, lno, msg, args, exc_info, func, extra, sinfo) self.handle(record) def handle(self, record): """ Call the handlers for the specified record. This method is used for unpickled records received from a socket, as well as those created locally. Logger-level filtering is applied. """ if (not self.disabled) and self.filter(record): self.callHandlers(record) def hasHandlers(self): """ See if this logger has any handlers configured. Loop through all handlers for this logger and its parents in the logger hierarchy. Return True if a handler was found, else False. Stop searching up the hierarchy whenever a logger with the "propagate" attribute set to zero is found - that will be the last logger which is checked for the existence of handlers. """ c = self rv = False while c: if c.handlers: rv = True break if not c.propagate: break else: c = c.parent return rv def callHandlers(self, record): """ Pass a record to all relevant handlers. Loop through all handlers for this logger and its parents in the logger hierarchy. If no handler was found, output a one-off error message to sys.stderr. Stop searching up the hierarchy whenever a logger with the "propagate" attribute set to zero is found - that will be the last logger whose handlers are called. """ c = self found = 0 while c: for hdlr in c.handlers: found = found + 1 if record.levelno >= hdlr.level: hdlr.handle(record) if not c.propagate: c = None #break out else: c = c.parent if (found == 0): if lastResort: if record.levelno >= lastResort.level: lastResort.handle(record) elif raiseExceptions and not self.manager.emittedNoHandlerWarning: sys.stderr.write("No handlers could be found for logger" " \"%s\"\n" % self.name) self.manager.emittedNoHandlerWarning = True
默认的,当通过logger.debug,logger.info的方式打印日志时,会先判断对应日志级别是否开启,如果开启,则调用logger实例的_log方法,接着经过一连串的函数调用(self._log() -> self.handle -> self.callHandlers),如上,self.callHandlers中,会先遍历当前日志打印器自身的所有日志处理器,处理日志消息,然后判断propagate属性是否为True,如果为True,则获取上级日志打印器,继续遍历其日志处理器,处理消息,否则不遍历上级
另外,查看hasHandlers函数可知,判断一个logger是否有日志处理器,也用到了propagate,如果propagate为True,则遍历父级日志打印器,看其是否存在日志处理器,如果父级或者父辈日志打印器存在日志处理器,则判断该logger拥有日志处理器。
由此可见,propagate功能就是用于控制是否向上遍历父辈日志打印器,进而控制当前日志打印器是否共享父辈打印器的日志处理器。