class A:
    def __getattr__(self, key):
        return key

a = A()
print( a.b )  # Output: b

navigator.__defineGetter__('userAgent', function(){
    return 'foo' // customized user agent
});

navigator.userAgent; // 'foo'

var o = {
  a:7,
  get b() { return this.a + 1; },
  set c(x) { this.a = x / 2; }
};