python - 为什么在解包元组时 var 类型会发生变化？

Question

考虑这个例子:

>>> t = (1, 2, 3)
>>> a, b, c = t
>>> a, b, c
(1, 2, 3)
>>> a, *b = t
>>> a, b
(1, [2, 3])

为什么在使用 a, *b = t 解包元组时得到的是列表而不是元组？

Answer 1

如 PEP 3132 中所述，这是扩展的可迭代拆包。类型不会“改变”；只是定义了 * 解包在所有情况下都会产生一个列表。

有人建议它产生:

• 元组而不是列表:

Make the starred target a tuple instead of a list. This would be consistent with a function's *args, but make further processing of the result harder.

• 与右侧相同的类型:

Try to give the starred target the same type as the source iterable, for example, b in a, *b = 'hello' would be assigned the string 'ello'. This may seem nice, but is impossible to get right consistently with all iterables.

最终，这些提议被否决了。

有关更多信息，请参阅 here和 here .