最近遇到个有关tuple的面试题，挺有意思的。
# 下面会输出什么？为什么
In [18]: tu = (1, [1, 2])
In [19]: tu[1].append(3)
In [20]: print(tu)
(1, [1, 2, 3])
tupple不可变是指对象不可变，不可以对tuple中的元素进行赋值操作。它所包含的元素的可变性取决于该元素的属性。1
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34 In [22]: tu[1] = [1,2,3,4]
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-22-1e2059dd0201> in <module>()
----> 1 tu[1] = [1,2,3,4]
TypeError: 'tuple' object does not support item assignment
In [23]: print(tu) #报错，赋值操作未成功
(1, [1, 2, 3])
In [24]: tu[1] += [1,2,3,4]
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-6-e1dc81ae6e45> in <module>
----> 1 tu[1] += [1,2,3,4]
TypeError: 'tuple' object does not support item assignment
In [25]: tu # 报错,虽然报错,但操作成功了
Out[26]: (1, [1, 2, 3, 1, 2, 3, 4])
In [27]: class A:
...: a = 1
...:
In [28]: a = A()
In [29]: t = (1, a)
In [30]: t[1].a = 2
In [31]: print(t[1].a)
2