logging源码实现

aa.py

#  logger.info('This is an info message')
#  Logger().info() --> ._log()  然后 -> .makeRecord()  # makeRecord 生成LogRecord对象,就是一条日志记录的对象
#  然后调用 Logger().handle(record)  ---> .callHandlers(record) 里面循环执行 hdlr.handle(record), 这个hdlr 就是MidnightRotatingFileHandler对象，
#  找MidnightRotatingFileHandler的 父类 handle方法的实现，一直找到Handler类里的下面这个

# def handle(self, record):
#     """
#     Conditionally emit the specified logging record.

#     Emission depends on filters which may have been added to the handler.
#     Wrap the actual emission of the record with acquisition/release of
#     the I/O thread lock. Returns whether the filter passed the record for
#     emission.
#     """
#     rv = self.filter(record)
#     if rv:
#         self.acquire()
#         try:
#             self.emit(record)
#         finally:
#             self.release()
#     return rv
#
#  就是调用emit()
#
#  继续找MidnightRotatingFileHandler父类的emit(), 在BaseRotatingHandler()里找到，是下面这样
#     def emit(self, record):
#        """
#        Emit a record.
#
#        Output the record to the file, catering for rollover as described
#        in doRollover().
#        """
#        try:
#           if self.shouldRollover(record):
#                self.doRollover()
#            logging.FileHandler.emit(self, record)
#        except Exception:
#            self.handleError(record)
#
# 
# 然后BaseRotatingHandler的emit调用FileHandler的emit 就是打开文件