本文详细分析了Python logging模块中的getLogger函数，包括其源码解析，介绍了如何根据指定名称获取或创建日志器，以及日志器的层级结构建立过程。通过对Manager和Logger类的理解，阐述了日志器的父级和子级如何关联，以及占位符PlaceHolder的作用。
日志打印之logging.getLogger源码分析
By:授客 QQ：1033553122
#实践环境
WIN 10
Python 3.6.5
#函数说明
logging.getLogger(name=None)
getLogger函数位于logging/__init__.py脚本
#源码分析
_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
结论：如函数注释所述，如果调用getLogger时，如果没有指定函数参数(即要获取的日志打印器名称)或者参数值不为真，则默认返回root打印器
##Logger.manager.getLogger(self, name)源码分析
该函数位于logging/__init__.py脚本
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
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