日志打印之logging.config.dictConfig使用总结
By:授客
#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：
代码语言：javascript复制 "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
代码语言：javascript复制study.py
#!/usr/bin/env python
# -*- coding:utf-8 -*-
'''
@CreateTime: 2020/12/29 14:08
@Author : shouke
'''
import logging
import logging.config
LOGGING_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
代码语言：javascript复制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
代码语言：javascript复制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。
