python-3.x – 为什么范围反转时range_iterator？

>>> r = range(4)
>>> r 
range(0,4)
>>> r[3]
3
>>> for i in r:
    print(i)

0
1
2
3
>>> list(r)
[0,1,2,3]

但是,如果我在相同的范围对象上调用reverse：

>>> r = reversed(range(4))
>>> r
<range_iterator object at memaddr>
>>> for i in r:
    print(i)
3
2
1
0
>>> r[3]
TypeError: 'range_iterator' object is not subscriptable         # ?
>>> range(r)
TypeError: 'range_iterator' cannot be interpreted as an integer # ?
>>> list(r)
[]          # ? uhmm

嗯……表现得像发电机但不太有用.

有没有理由反转范围对象不像正常的生成器/迭代器那样嘎嘎叫？