使用python logging的配置

使用python logging的配置

简介

在python中使用logging模块，对log进行配置时，可以使用配置文件，而不用再python源码中进行配置。
这样方便更改logging的配置。

---

使用basicConfig进行配置

使用logging.basicConfig来加载配置文件。

import logging  

LOG_FILENAME="myapp.log"  
logging.basicConfig(filename=LOG_FILENAME,level=logging.DEBUG)  

logging.debug("this is a debugmsg!")    
logging.info("this is a infomsg!")    
logging.warn("this is a warn msg!")    
logging.error("this is a error msg!")    
logging.critical("this is a critical msg!")  

---

使用config.fileConfig进行配置

使用logging.config.fileConfig来加载配置文件。

import logging
import logging.config

# 加载配置文件
logging.config.fileConfig("logging2.conf")

#create logger
logger = logging.getLogger("simpleExample") 
## getLogger中的参数如果在配置文件中找不到，则缺省使用root配置。


## log 
logger.debug("debug message")
logger.info("info message")
logger.warn("warn message")
logger.error("error message")
logger.critical("critical message")

---

可以看看fileConfig的具体定义：

def fileConfig(fname, defaults=None, disable_existing_loggers=True):
    """
    Read the logging configuration from a ConfigParser-format file.

    This can be called several times from an application, allowing an end user
    the ability to select from various pre-canned configurations (if the
    developer provides a mechanism to present the choices and load the chosen
    configuration).
    """
    import ConfigParser

    cp = ConfigParser.ConfigParser(defaults)
    if hasattr(fname, 'readline'):
        cp.readfp(fname)
    else:
        cp.read(fname)

    formatters = _create_formatters(cp)

    # critical section
    logging._acquireLock()
    try:
        logging._handlers.clear()
        del logging._handlerList[:]
        # Handlers add themselves to logging._handlers
        handlers = _install_handlers(cp, formatters)
        _install_loggers(cp, handlers, disable_existing_loggers)
    finally:
        logging._releaseLock()

---

配置文件

这里是示例的配置文件

[loggers]
keys=root,simpleExample

[handlers]
keys=consoleHandler,fileHandler

[formatters]
keys=simpleFormatter

[logger_root]
level=DEBUG
handlers=fileHandler

[logger_simpleExample]
level=DEBUG
handlers=consoleHandler,fileHandler
qualname=simpleExample
propagate=0

[handler_consoleHandler]
class=StreamHandler
level=WARNING
formatter=simpleFormatter
args=(sys.stdout,)

[handler_fileHandler]
class=FileHandler
level=DEBUG
formatter=simpleFormatter
args=('testbyconfig.log','a+')

[formatter_simpleFormatter]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=

配置说明[loggers]

在loggers中使用keys定义几个logger，在code中使用。

[loggers]
keys=root,simpleExample

实践中需要注意的是，一般root强制定义。在code中getLogger(“loggerName”)如果不匹配loggerName时，会使用root。

具体的logger项目配置section，使用的section名以logger_连接上具体的名称。如logger_root, logger_simpleExample。

这里是logging中的实现代码

#---------------------------------------------------------------------------
# Utility functions at module level.
# Basically delegate everything to the root logger.
#---------------------------------------------------------------------------

def getLogger(name=None):
    """
    Return a logger with the specified name, creating it if necessary.

    If no name is specified, return the root logger.
    """
    if name:
        return Logger.manager.getLogger(name)
    else:
        return root


# ... ...

class Manager(object):
    """
    There is [under normal circumstances] just one Manager instance, which
    holds the hierarchy of loggers.
    """
    def __init__(self, rootnode):
        """
        Initialize the manager with the root node of the logger hierarchy.
        """
        self.root = rootnode
        self.disable = 0
        self.emittedNoHandlerWarning = 0
        self.loggerDict = {}
        self.loggerClass = None

    def getLogger(self, name):
        """
        Get a logger with the specified name (channel name), creating it
        if it doesn't yet exist. This name is a dot-separated hierarchical
        name, such as "a", "a.b", "a.b.c" or similar.

        If a PlaceHolder existed for the specified name [i.e. the logger
        didn't exist but a child of it did], replace it with the created
        logger and fix up the parent/child references which pointed to the
        placeholder to now point to the logger.
        """
        rv = None
        if not isinstance(name, basestring):
            raise TypeError('A logger name must be string or Unicode')
        if isinstance(name, unicode):
            name = name.encode('utf-8')
        _acquireLock()
        try:
            if name in self.loggerDict:
                rv = self.loggerDict[name]
                if isinstance(rv, PlaceHolder):
                    ph = rv
                    rv = (self.loggerClass or _loggerClass)(name)
                    rv.manager = self
                    self.loggerDict[name] = rv
                    self._fixupChildren(ph, rv)
                    self._fixupParents(rv)
            else:
                rv = (self.loggerClass or _loggerClass)(name)
                rv.manager = self
                self.loggerDict[name] = rv
                self._fixupParents(rv)
        finally:
            _releaseLock()
        return rv


    #... ...

配置说明[logger_name]

在这里配置要使用的logger-handlers： 可以使用consoleHandler，fileHandler……。

配置说明[handler_handlerName]

在这里配置要使用logger的handlers的对应的配置.
如class、format、level及对应的args;args是传入class函数的参数。

如consoleHandler对应了

class=StreamHandler
level=WARNING
formatter=simpleFormatter
args=(sys.stdout,)

而 handler_fileHandler 对应的配置

class=FileHandler
level=DEBUG
formatter=simpleFormatter
args=('testbyconfig.log','a+')

配置说明[formatter_simpleFormatter]

这里配置日志的formatter，如：

format=%(asctime)s - %(name)s - %(levelname)s - %(message)s