python3 logging 句柄释放 shutdown 简介

一种场景：python开发中使用logging库记录日志信息。在程序结束前需要将日志转存到一个备份存储并删除现有日志。但是删除日志时通常会报错，错误如下：

python.exe test.py
Traceback (most recent call last):
  File "C:/Users/sunday/Desktop/test/test.py", line 58, in <module>
    os.remove(log_file)
PermissionError: [WinError 32] 另一个程序正在使用此文件，进程无法访问。: 'C:\\Users\\sunday\\Desktop\\test\\test.log'

无法删除的原因就是logging没有释放日志文件的句柄，造成没权限删除。这时候logging库的shutdown就派上用场。查看shutdown源码可以看到shutdown就是用于程序退出前被使用。

def shutdown(handlerList=_handlerList):
    """
    Perform any cleanup actions in the logging system (e.g. flushing
    buffers).

    Should be called at application exit.
    """
    for wr in reversed(handlerList[:]):
        #errors might occur, for example, if files are locked
        #we just ignore them if raiseExceptions is not set
        try:
            h = wr()
            if h:
                try:
                    h.acquire()
                    h.flush()
                    h.close()
                except (OSError, ValueError):
                    # Ignore errors which might be caused
                    # because handlers have been closed but
                    # references to them are still around at
                    # application exit.
                    pass
                finally:
                    h.release()
        except: # ignore everything, as we're shutting down
            if raiseExceptions:
                raise
            #else, swallow

#Let's try and shutdown automatically on application exit...
import atexit
atexit.register(shutdown)

删除日志文件前加上shutdown，完美退出。

logging.shutdown()
os.remove(log_file)

执行：
python.exe test.py

进程已结束，退出代码 0