为什么Python中的元组可以反转但没有__reversed__？

问题描述

在讨论时，我们意识到元组没有 __颠倒__ 方法。我的猜测是创建迭代器需要改变元组。然而，元组在反转时可以正常运行。为什么反转的方法不能用于 __ reverse __ ？

In discussion of this answer we realized that tuples do not have a __reversed__ method. My guess was that creating the iterator would require mutating the tuple. And yet tuples play fine with reversed. Why can't the approach used for reversed be made to work for __reversed__ as well?

>>> foo = range(3)
>>> foo
[0, 1, 2]
>>> list(foo.__reversed__())
[2, 1, 0]
>>> foo
[0, 1, 2]
>>> bar = (0, 1, 2)
>>> list(bar.__reversed__())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'tuple' object has no attribute '__reversed__'
>>> reversed(bar)
<reversed object at 0x10603b310>
>>> tuple(reversed(bar))
(2, 1, 0)

推荐答案

根据：

反转（seq）

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