偶数列表? [英] Even numbers a list?

问题描述

如何创建列表，仅提取或搜索该列表中的偶数?

How do I create a list and only extract or search out the even numbers in that list?

创建一个函数even_only(l)，该函数将整数列表作为唯一参数.这 函数将返回一个新列表，其中包含l的所有(且仅)元素，这些元素可以被2整除.原始列表l应当保持不变.

Create a function even_only(l) that takes a list of integers as its only argument. The function will return a new list containing all (and only) the elements of l which are evenly divisible by 2. The original list l shall remain unchanged.

例如，even_only([1, 3, 6, 10, 15, 21, 28])应该返回[6, 10, 28]，并且 even_only([1, 4, 9, 16, 25])应该返回[4, 16].

For examples, even_only([1, 3, 6, 10, 15, 21, 28]) should return [6, 10, 28], and even_only([1, 4, 9, 16, 25]) should return [4, 16].

提示:首先创建一个空列表，每当遇到偶数时，将其添加到列表中，最后返回列表.

Hint: Start by creating an empty list, and whenever you encounter an even number in it, add it to your list, then at the end, return your list.

推荐答案

手动":

def even_only(lst):
    evens = []
    for number in lst:
        if is_even(number):
            evens.append(number)
    return evens

Pythonic:

def even_only(iter):
    return [x for x in iter if is_even(x)]

由于是家庭作业，因此您可以填写is_even函数.

Since it's homework, you can fill in the is_even function.

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