python 权限判断问题

[mdjxyz]

def can(self, permissions):
return self.role is not None and \
(self.role.permissions & permissions) == permissions

我想问下直接用self.role.permissions==permissions 不可以吗为什么要用
        (self.role.permissions & permissions) == permissions 优点在哪里

[MartinWu]

依我愚见，(self.role.permissions & permissions) == permissions 等同于 permissions is not None and self.role.permissions==permissions

[realityone]

self.role.permissions = 0xFFFFFFFF
permissions = 0x0000FFFF

self.role.permissions != permissions
(self.role.permissions & permissions) = permissions