从嵌套列表的子列表中提取第一个和最后一个元素 [英] Extracting first and last element from sublists in nested list

问题描述

如何从嵌套列表中的每个子列表中提取第一个和最后一个元素?

How do you extract the first and last elements from each sublist in a nested list?

例如:

x=[[1, 2, 3], [4, 5, 6], [7, 8, 9]]
print(x)
#[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

期望的结果-

[[1, 3], [4, 6], [7, 9]]

这是我见过的最接近的地方-

This is the closest I've seen-

a = [x[i][i] for i in (0, -1)]
print(a)
#[1, 9]

推荐答案

您有正确的想法.如果列表中的列表仅深一层，则可以像尝试尝试的那样使用列表理解和-1索引访问第一个和最后一个元素:

You have the right idea. If your list inside list is only one layer deep, you can access the first and last elements with a list comprehension and -1 indexing like you were trying to do:

a = [[sublist[0],sublist[-1]] for sublist in x]

输出:

>>> a
[[1, 3], [4, 6], [7, 9]]

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