Python列表理解-简单 [英] Python list comprehension - simple

问题描述

我有一个列表，我只想在满足特定条件的条目上使用某些功能，而其他条目保持不变.

I have a list and I want to use a certain function only on those entries of it that fulfills a certain condition - leaving the other entries unmodified.

示例:假设我只想将偶数个元素乘以2.

Example: Say I want to multiply by 2 only those elements who are even.

a_list = [1, 2, 3, 4, 5]

想要的结果:

a_list => [1, 4, 3, 8, 5]

但是[elem * 2 for elem in a_list if elem %2 == 0]会产生[4, 8](它还充当过滤器).

But [elem * 2 for elem in a_list if elem %2 == 0] yields [4, 8] (it acted as a filter in addition).

正确的解决方法是什么?

What is the correct way to go about it?

推荐答案

使用条件表达式:

[x * 2 if x % 2 == 0 else x
 for x in a_list]

(数学怪人的注:您也可以通过以下方式解决这种特殊情况

(Math geek's note: you can also solve this particular case with

[x * (2 - x % 2) for x in a_list]

但是无论如何我还是希望第一个选项;)

but I'd prefer the first option anyway ;)

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