python日志记录会刷新每个日志吗？

Question

当我使用标准模块 logging 将日志写入文件时，是否将每个日志分别刷新到磁盘？例如，以下代码是否会将日志刷新10次？

logging.basicConfig(level=logging.DEBUG, filename='debug.log')
    for i in xrange(10):
        logging.debug("test")

如果是这样，它会变慢吗？

Answer 1

是的，它会在每次调用时刷新输出。您可以在的源代码中看到StreamHandler：

def flush(self):
    """
    Flushes the stream.
    """
    self.acquire()
    try:
        if self.stream and hasattr(self.stream, "flush"):
            self.stream.flush()
    finally:
        self.release()

def emit(self, record):
    """
    Emit a record.

    If a formatter is specified, it is used to format the record.
    The record is then written to the stream with a trailing newline.  If
    exception information is present, it is formatted using
    traceback.print_exception and appended to the stream.  If the stream
    has an 'encoding' attribute, it is used to determine how to do the
    output to the stream.
    """
    try:
        msg = self.format(record)
        stream = self.stream
        stream.write(msg)
        stream.write(self.terminator)
        self.flush()   # <---
    except (KeyboardInterrupt, SystemExit): #pragma: no cover
        raise
    except:
        self.handleError(record)

我真的不会介意日志记录的性能，至少在分析和发现它是瓶颈之前不会。无论如何，您始终可以创建一个在每次调用时都Handler不会执行的子类（即使如果发生严重异常/解释器崩溃，也可能会丢失大量日志）。flush``emit