os.chmod(path,mode)   这个方法应该很简单，只需要2个参数，一个是路径，一个是说明路径的模式，下面列出了这个用法中可以使用的一些常用的模式：stat.S_ISUID: Set user ID on execution.                      不常用stat.S_ISGID: Set group ID on execution.                    不常用stat.S_ENFMT: Record locking enforced.                                          不常用stat.S_ISVTX: Save text image after execution.                                在执行之后保存文字和图片stat.S_IREAD: Read by owner.                                                           对于拥有者读的权限stat.S_IWRITE: Write by owner.                                                         对于拥有者写的权限stat.S_IEXEC: Execute by owner.                                                       对于拥有者执行的权限stat.S_IRWXU: Read, write, and execute by owner.                          对于拥有者读写执行的权限stat.S_IRUSR: Read by owner.                                                            对于拥有者读的权限stat.S_IWUSR: Write by owner.                                                          对于拥有者写的权限stat.S_IXUSR: Execute by owner.                                                       对于拥有者执行的权限stat.S_IRWXG: Read, write, and execute by group.                           对于同组的人读写执行的权限stat.S_IRGRP: Read by group.                                                             对于同组读的权限stat.S_IWGRP: Write by group.                                                           对于同组写的权限stat.S_IXGRP: Execute by group.                                                        对于同组执行的权限stat.S_IRWXO: Read, write, and execute by others.                          对于其他组读写执行的权限stat.S_IROTH: Read by others.                                                           对于其他组读的权限stat.S_IWOTH: Write by others.                                                         对于其他组写的权限stat.S_IXOTH: Execute by others.                                                      对于其他组执行的权限