_loggerClass = Logger
# ...略
 
root = RootLogger(WARNING)
Logger.root = root
Logger.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

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 = Logger
        rv.manager = self
        self.loggerDict[name] = rv
        self._fixupParents(rv)
    finally:
      _releaseLock()
    return rv

_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

# _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
    i = name.rfind(".")
    rv = None # 存放alogger日志打印器的上級日志打印器
    while (i > 0) and not rv: # 如果名稱中存在英文的點，并且找到上級日志打印器
      substr = name[:i] # 獲取名稱中位于最后一個英文的點的左側(cè)字符串（暫且稱至為 點分上級）
      if substr not in self.loggerDict: # 如果 點分上級 不存在日志打印器字典中
        self.loggerDict[substr] = PlaceHolder(alogger) # 創(chuàng)建PlaceHolder實例作為 點分上級 對應(yīng)的日志打印器 # 繼續(xù)查找點分上級日志打印器 # 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，暫且稱之為PlaceHolder日志打印器
      else: # 否則
        obj = self.loggerDict[substr] # 獲取 點分上級 對應(yīng)的日志打印器
        if isinstance(obj, Logger): # 如果為Logger實例，如果是，則跳出循環(huán)，執(zhí)行 # 為日志打印器設(shè)置上級
          rv = obj
        else: # 否則
          assert isinstance(obj, PlaceHolder) # 斷言它為PlaceHolder的實例
          obj.append(alogger) # 把日志打印器添加為點分上級對應(yīng)的PlaceHolder日志打印器實例的下級日志打印器 執(zhí)行 # 繼續(xù)查找點分上級日志打印器
      i = name.rfind(".", 0, i - 1) # 繼續(xù)查找點分上級日志打印器
    if not rv: # 找不到點分上級、或者遍歷完所有點分上級，都沒找到上級日志打印器
      rv = self.root # 則 把root日志打印器設(shè)置為alogger日志打印器的上級日志打印器
    alogger.parent = rv # 為日志打印器設(shè)置上級
 
 
 
  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
    namelen = len(name) # 獲取日志打印器名稱長度
    for c in ph.loggerMap.keys(): # 遍歷獲取的PlaceHolder日志打印器實例的子級日志打印器
      #The if means ... if not c.parent.name.startswith(nm)
      if c.parent.name[:namelen] != name: # 如果PlaceHolder日志打印器實例名稱不以alogger日志打印器名稱為前綴，
        alogger.parent = c.parent # 那么，設(shè)置alogger日志打印器的上級日志打印器為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PlaceHolder日志打印器的上級