如何将两个列表合并为多个列表的列表? [英] How to merge two lists into a list of multiple lists?

问题描述

给出两个列表lst1和lst2:

Given two lists lst1 and lst2:

lst1 = ['a']
lst2 = [['b'],
        ['b', 'c'],
        ['b', 'c', 'd']]

我想将它们合并为具有所需输出的多个列表的列表，如下所示:

I'd like to merge them into a list of multiple lists with a desired output like this:

desiredList = [['a', ['b']],
              ['a', ['b', 'c']],
              ['a', ['b', 'c', 'd']]]

这是我使用 lst1 + lst2 和 list.append()进行的尝试之一:

Here is one of my attempts that comes close using lst1 + lst2 and list.append():

lst3 = []
for elem in lst2:
    new1 = lst1
    new2 = elem
    theNew = new1 + new2
    lst3.append(theNew)

print(lst3)

#Output:
#[['a', 'b'],
#['a', 'b', 'c'],
#['a', 'b', 'c', 'd']]

对此进行扩展，我认为 theNew = new1.append(new2)的另一个变体可以解决问题.但是没有:

Expanding on this, I thought another variation with theNew = new1.append(new2)would do the trick. But no:

lst3 = []
for elem in lst2:
    new1 = lst1
    new2 = elem
    #print(new1 + new2)
    #theNew = new1 + new2
    theNew = new1.append(new2)

    lst3.append(theNew)
print(lst3)

# Output:
[None, None, None]

通过 extend ，您将获得相同的结果.

And you'll get the same result with extend.

我想这应该很容易，但是我很茫然.

I guess this should be really easy, but I'm at a loss.

谢谢您的任何建议！

推荐答案

您可以使用带有 fillvalue 的 itertools.zip_longest 实现所需的输出:

You could achieve your desired output with itertools.zip_longest with a fillvalue:

>>> from itertools import zip_longest
>>> list(zip_longest(lst1, lst2, fillvalue=lst1[0]))
[('a', ['b']), ('a', ['b', 'c']), ('a', ['b', 'c', 'd'])]

或者如果您需要列表列表:

Or if you need a list of lists:

>>> [list(item) for item in zip_longest(lst1, lst2, fillvalue=lst1[0])]
[['a', ['b']], ['a', ['b', 'c']], ['a', ['b', 'c', 'd']]]

请注意，这假设 lst1 始终包含单个元素，如您的示例一样.

Note this assumes that lst1 always contains a single element as in your example.

这篇关于如何将两个列表合并为多个列表的列表?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！