python - 如果Python切片复制引用，为什么我不能用它来修改原始列表？

Question

我知道Slicing lists does not generate copies of the objects in the list; it just copies the references to them.

但如果是这样，那为什么这行不通呢？

l = [1, 2, 3]

# Attempting to modify the element at index 1
l[0:2][-1] = 10

# but the attempt fails. The original list is unchanged
l
> [1, 2, 3]

不应该l[0:2][-1]指向原始列表索引 1 处的元素？

Answer 1

切片 list返回一个新的浅拷贝 list目的。虽然您没有对原始列表的项目进行深度复制是正确的，但结果是一个全新的 list区别于原版。

见 Python 3 tutorial :

All slice operations return a new list containing the requested elements. This means that the following slice returns a shallow copy of the list:

>>> squares = [1, 4, 9, 16, 25]
>>> squares[:]
[1, 4, 9, 16, 25]

考虑

>>> squares[:] is squares
False