問題描述

假設我有一個這樣的 Python 列表:

Say I have a Python list like this:

letters = ['a','b','c','d','e','f','g','h','i','j']

我想在每個第 n 個元素之后插入一個x"，比如說該列表中的三個字符.結果應該是:

I want to insert an 'x' after every nth element, let's say three characters in that list. The result should be:

letters = ['a','b','c','x','d','e','f','x','g','h','i','x','j']

我知道我可以通過循環和插入來做到這一點.我真正在尋找的是一種 Python 方式，也許是單線?

I understand that I can do that with looping and inserting. What I'm actually looking for is a Pythonish-way, a one-liner maybe?

推薦答案

我有兩個一體機.

給定:

>>> letters = ['a','b','c','d','e','f','g','h','i','j']

1. 使用enumerate獲取索引，每3^rd個字母添加'x'，eg: mod(n, 3) == 2，然后拼接成字符串并list().

1. Use enumerate to get index, add 'x' every 3^rd letter, eg: mod(n, 3) == 2, then concatenate into string and list() it.

>>> list(''.join(l + 'x' * (n % 3 == 2) for n, l in enumerate(letters)))

['a', 'b', 'c', 'x', 'd', 'e', 'f', 'x', 'g', 'h', 'i', 'x', 'j']

但是作為 @sancho.s 指出如果任何元素有多個字母，這將不起作用.

But as @sancho.s points out this doesn't work if any of the elements have more than one letter.

使用嵌套推導來展平列表列表^(a)，以 3 個為一組進行切片，如果距離末尾小于 3，則添加 'x'列表.

Use nested comprehensions to flatten a list of lists^(a), sliced in groups of 3 with 'x' added if less than 3 from end of list.

>>> [x for y in (letters[i:i+3] + ['x'] * (i < len(letters) - 2) for
     i in xrange(0, len(letters), 3)) for x in y]

['a', 'b', 'c', 'x', 'd', 'e', 'f', 'x', 'g', 'h', 'i', 'x', 'j']

(a) [item for subgroup in groups for item in subgroup] 展平一個鋸齒狀的列表列表.

(a) [item for subgroup in groups for item in subgroup] flattens a jagged list of lists.

這篇關于在每個第 n 個元素之后插入 Python 列表中的元素的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！