1、os.chmod()方法 此方法通过数值模式更新路径或文件权限。该模式可采取下列值或按位或运算组合之一：
stat.S_ISUID: Set user ID on execution.
stat.S_ISGID: Set group ID on execution.
stat.S_ENFMT: Record locking enforced.
stat.S_ISVTX: Save text image after execution.
stat.S_IREAD: Read by owner.
stat.S_IWRITE: Write by owner.
stat.S_IEXEC: Execute by owner.
stat.S_IRWXU: Read, write, and execute by owner.
stat.S_IRUSR: Read by owner.
stat.S_IWUSR: Write by owner.
stat.S_IXUSR: Execute by owner.
stat.S_IRWXG: Read, write, and execute by group.
stat.S_IRGRP: Read by group.
stat.S_IWGRP: Write by group.
stat.S_IXGRP: Execute by group.
stat.S_IRWXO: Read, write, and execute by others.
stat.S_IROTH: Read by others.
stat.S_IWOTH: Write by others.
stat.S_IXOTH: Execute by others.
2、语法：
os.chmod(path, mode);
3、参数：
path: This is the path for which mode would be set.
mode: This may take one of the above mentioned values or bitwise ORedcombinations of them:
