py3.py 文件源码

def truncate(self, size=-1):
        if size == -1:
            size = self.tell()
        try:
            rv = _original_os.ftruncate(self._fileno, size)
        except OSError as e:
            raise IOError(*e.args)
        else:
            self.seek(size)  # move position&clear buffer
            return rv