實(shí)踐環(huán)境

WIN 10

Python 3.6.5

函數(shù)說(shuō)明

logging.getLogger(name=None)

getLogger函數(shù)位于logging/__init__.py腳本

源碼分析

_loggerClass = Logger# ...略 root = RootLogger(WARNING)Logger.root = rootLogger.manager = Manager(Logger.root) # ...略 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

結(jié)論：如函數(shù)注釋所述，如果調(diào)用getLogger時(shí)，如果沒(méi)有指定函數(shù)參數(shù)(即要獲取的日志打印器名稱(chēng))或者參數(shù)值不為真，則默認(rèn)返回root打印器

Logger.manager.getLogger(self, name)源碼分析

該函數(shù)位于logging/__init__.py腳本

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 = False self.loggerDict = {} self.loggerClass = None self.logRecordFactory = 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, str): raise TypeError(’A logger name must be a string’) _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) # _loggerClass = Loggerrv.manager = selfself.loggerDict[name] = rvself._fixupParents(rv) finally: _releaseLock() return rvLogger源碼分析

_nameToLevel = { ’CRITICAL’: CRITICAL, ’FATAL’: FATAL, ’ERROR’: ERROR, ’WARN’: WARNING, ’WARNING’: WARNING, ’INFO’: INFO, ’DEBUG’: DEBUG, ’NOTSET’: NOTSET,} # ...略 def _checkLevel(level): if isinstance(level, int): rv = level elif str(level) == level: if level not in _nameToLevel: raise ValueError('Unknown level: %r' % level) rv = _nameToLevel[level] else: raise TypeError('Level not an integer or a valid string: %r' % level) return rv # ...略class PlaceHolder(object): ''' PlaceHolder instances are used in the Manager logger hierarchy to take the place of nodes for which no loggers have been defined. This class is intended for internal use only and not as part of the public API. ''' def __init__(self, alogger): ''' Initialize with the specified logger being a child of this placeholder. ''' self.loggerMap = { alogger : None } def append(self, alogger): ''' Add the specified logger as a child of this placeholder. ''' if alogger not in self.loggerMap: self.loggerMap[alogger] = None class Logger(Filterer): ''' Instances of the Logger class represent a single logging channel. A 'logging channel' indicates an area of an application. Exactly how an 'area' is defined is up to the application developer. Since an application can have any number of areas, logging channels are identified by a unique string. Application areas can be nested (e.g. an area of 'input processing' might include sub-areas 'read CSV files', 'read XLS files' and 'read Gnumeric files'). To cater for this natural nesting, channel names are organized into a namespace hierarchy where levels are separated by periods, much like the Java or Python package namespace. So in the instance given above, channel names might be 'input' for the upper level, and 'input.csv', 'input.xls' and 'input.gnu' for the sub-levels. There is no arbitrary limit to the depth of nesting. ''' def __init__(self, name, level=NOTSET): ''' Initialize the logger with a name and an optional level. ''' Filterer.__init__(self) self.name = name self.level = _checkLevel(level) self.parent = None self.propagate = True self.handlers = [] self.disabled = False # ... 略

結(jié)論：如果調(diào)用logging.getLogger()時(shí)，有指定日志打印器名稱(chēng)，且名稱(chēng)為真(不為空字符串，0，F(xiàn)alse等False值)，

1）如果名稱(chēng)為不存在的日志打印器名稱(chēng)，則，且參數(shù)值為真，但是即要獲取的日志打印器名稱(chēng))或者參數(shù)值不為真，則創(chuàng)建一個(gè)名為給定參數(shù)值的日志打印器，該日志打印器，默認(rèn)級(jí)別默認(rèn)為NOTSET，disable_existing_loggers配置為False，propagate配置為T(mén)rue。然后在日志打印器字典中記錄該名稱(chēng)和日志打印器的映射關(guān)系，接著調(diào)用 _fixupParents(創(chuàng)建的日志打印器實(shí)例)類(lèi)實(shí)例方法--為日志打印器設(shè)置上級(jí)日志打印器，最后返回該日志打印器。

2）如果名稱(chēng)已存在日志打印器名稱(chēng)，則獲取該日志打印器，然后判斷日志打印器是否為PlaceHolder類(lèi)實(shí)例，如果是，則創(chuàng)建一個(gè)名為所給參數(shù)值的日志打印器，同第1）點(diǎn)，該日志打印器，默認(rèn)級(jí)別默認(rèn)為NOTSET，disable_existing_loggers配置為False，propagate配置為T(mén)rue。然后在日志打印器字典中記錄該名稱(chēng)和日志打印器的映射關(guān)系，接著調(diào)用 _fixupParents(創(chuàng)建的打印器實(shí)例)類(lèi)實(shí)例方法，_fixupChildren(PlaceHolder類(lèi)實(shí)例--根據(jù)名稱(chēng)獲取的日志打印器，新建的日志打印器實(shí)例)--為新建日志打印器設(shè)置上級(jí)日志打印器，為PlaceHolder類(lèi)實(shí)例現(xiàn)有下級(jí)PlaceHolder日志打印器實(shí)例重新設(shè)置上級(jí)日志打印器，最后返回該日志打印器。

_fixupParents及_fixupChildren函數(shù)源碼分析

# _fixupParents # ...略class Manager(object): # ...略 def _fixupParents(self, alogger): ''' Ensure that there are either loggers or placeholders all the way from the specified logger to the root of the logger hierarchy. ''' name = alogger.name # 獲取日志打印器名稱(chēng) i = name.rfind('.') rv = None # 存放alogger日志打印器的上級(jí)日志打印器 while (i > 0) and not rv: # 如果名稱(chēng)中存在英文的點(diǎn)，并且找到上級(jí)日志打印器 substr = name[:i] # 獲取名稱(chēng)中位于最后一個(gè)英文的點(diǎn)的左側(cè)字符串（暫且稱(chēng)至為 點(diǎn)分上級(jí)） if substr not in self.loggerDict: # 如果 點(diǎn)分上級(jí) 不存在日志打印器字典中self.loggerDict[substr] = PlaceHolder(alogger) # 創(chuàng)建PlaceHolder實(shí)例作為 點(diǎn)分上級(jí) 對(duì)應(yīng)的日志打印器 # 繼續(xù)查找點(diǎn)分上級(jí)日志打印器 # 注意，這里的PlaceHolder僅是占位用，不是真的打印器，這里為了方便描述，暫且稱(chēng)之為PlaceHolder日志打印器 else: # 否則obj = self.loggerDict[substr] # 獲取 點(diǎn)分上級(jí) 對(duì)應(yīng)的日志打印器if isinstance(obj, Logger): # 如果為L(zhǎng)ogger實(shí)例，如果是，則跳出循環(huán)，執(zhí)行 # 為日志打印器設(shè)置上級(jí) rv = objelse: # 否則 assert isinstance(obj, PlaceHolder) # 斷言它為PlaceHolder的實(shí)例 obj.append(alogger) # 把日志打印器添加為點(diǎn)分上級(jí)對(duì)應(yīng)的PlaceHolder日志打印器實(shí)例的下級(jí)日志打印器 執(zhí)行 # 繼續(xù)查找點(diǎn)分上級(jí)日志打印器 i = name.rfind('.', 0, i - 1) # 繼續(xù)查找點(diǎn)分上級(jí)日志打印器 if not rv: # 找不到點(diǎn)分上級(jí)、或者遍歷完所有點(diǎn)分上級(jí)，都沒(méi)找到上級(jí)日志打印器 rv = self.root # 則 把root日志打印器設(shè)置為alogger日志打印器的上級(jí)日志打印器 alogger.parent = rv # 為日志打印器設(shè)置上級(jí) def _fixupChildren(self, ph, alogger): ''' Ensure that children of the placeholder ph are connected to the specified logger. ''' name = alogger.name # 獲取日志打印器名稱(chēng) namelen = len(name) # 獲取日志打印器名稱(chēng)長(zhǎng)度 for c in ph.loggerMap.keys(): # 遍歷獲取的PlaceHolder日志打印器實(shí)例的子級(jí)日志打印器 #The if means ... if not c.parent.name.startswith(nm) if c.parent.name[:namelen] != name: # 如果PlaceHolder日志打印器實(shí)例名稱(chēng)不以alogger日志打印器名稱(chēng)為前綴，alogger.parent = c.parent # 那么，設(shè)置alogger日志打印器的上級(jí)日志打印器為PlaceHolder日志打印器c.parent = alogger # 設(shè)置alogger日志打印器為PlaceHolder日志打印器原有下級(jí)PlaceHolder日志打印器的上級(jí)

結(jié)論：日志打印器都是分父子級(jí)的，這個(gè)父子層級(jí)是怎么形成的，參見(jiàn)上述函數(shù)代碼注解

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