backports.py 文件源码

def concurrency_safe_rename(src, dst):
        """Renames ``src`` into ``dst`` overwriting ``dst`` if it exists.

        On Windows os.replace (or for Python 2.7 its implementation
        through MoveFileExW) can yield permission errors if executed by
        two different processes.
        """
        max_sleep_time = 1
        total_sleep_time = 0
        sleep_time = 0.001
        while total_sleep_time < max_sleep_time:
            try:
                replace(src, dst)
                break
            except Exception as exc:
                if getattr(exc, 'winerror', None) == error_access_denied:
                    time.sleep(sleep_time)
                    total_sleep_time += sleep_time
                    sleep_time *= 2
                else:
                    raise
        else:
            raise