对列表列表进行排序Python [英] Sort List of Lists of Lists Python

问题描述

我在python中有一个列表列表.我需要根据最低级别中的值之一对最高级别的列表进行排序.

I have a List of Lists of Lists in python. I need to sort the highest level of lists based on one of the values in the lowest levels.

对于玩具模型，我的列表首先创建为列表small，该列表是一个包含三个项的列表:

For a toy model, my list is created first with list small, which is a list containing lists with three items each:

    small = [["dog", 5, 6], ["cat", 391, 130], ["pig", 45, 2]...]`

然后有一个较大的列表large，该列表是通过将较小的列表和另一项附加在一起而创建的:

Then there is a larger list, large, that is created by appending the small list and another item together:

    large.append([["category 1"], small])`

这是在循环中完成的，因此，如果循环的计数器为5，它将通过创建列表small的函数进行5次，每次将其添加到列表large中.

This is done in a loop, so if the loop has a counter of 5, it will proceed through a function that creates a list small 5 times, each time, appending it to list large.

我的目标是根据最小列表(包含small列表的列表)中的元素对最终列表进行排序.我目前正在逐行打印large列表，其中small列表由其中的列表的index 1排序(请参阅:顺序为5、10、15，顺序为1、3、6，等)，所以我的输出是这样的:

My goal is to sort the final list based on an element in the smallest list (the list that comprises the small list). I am currently printing the large list out line by line, with the small list ordered by the index 1 of the lists within it (see: 5,10,15 in order, 1,3,6 in order, etc), so my output is this:

    >category 1:
    >['Dog', 5, 6]
    >['Pig', 10, 2]
    >['Cat', 15, 130]
    >['Buffalo', 20, 1]
    >['Newt', 25, 45]

    >category 2:
    >['Newt', 1, 1092]
    >['Cat', 3, 352]
    >['Pig', 6, 34]
    >['Buffalo', 9, 12]
    >['Dog', 12, 5]

    >category 3:
    >['Buffalo', 2, 12]
    >['Pig', 4, 37]
    >['Cat', 6, 34]
    >['Newt', 8, 150]
    >['Dog', 10, 52]

但是，当我查看组成最小数组的列表中index 1中的元素时，我想按最小到最大的顺序打印large列表.所以我的理想输出是这样:

However, i would like to print the large list in order of smallest to largest when looking at the element in index 1 in the list that makes up the smallest array. So my ideal output would be this:

    >category 2:
    >['Newt', 1, 1092]
    >['Cat', 3, 352]
    >['Pig', 6, 34]
    >['Buffalo', 9, 12]
    >['Dog', 12, 5]

    >category 3:
    >['Buffalo', 2, 12]
    >['Pig', 4, 37]
    >['Cat', 6, 34]
    >['Newt', 8, 150]
    >['Dog', 10, 52]

    >category 1:
    >['Dog', 5, 6]
    >['Pig', 10, 2]
    >['Cat', 15, 130]
    >['Buffalo', 20, 1]
    >['Newt', 25, 45]

我尝试用itemgetter()进行排序，但是，当用itemgetter()进行large排序时，我只能对列表large中的项目进行排序，这些项目是[category x]和[[a,b,c], [a,b,c]].有没有办法访问itemgetter的最低级别的元素?或对列表进行排序的另一种方法?

I have tried sorting with itemgetter(), however, when sorting large with itemgetter(), i can only sort the items in list large, which are [category x] and [[a,b,c], [a,b,c]]. Is there a way to access the lowest level of elements for itemgetter? or another way to go about sorting this list?

谢谢.

推荐答案

这可以一行完成:

sorted_large = sorted(large, key=lambda item: item[1][0][1])

sorted 内置函数采用key参数:

key指定一个参数的函数，该参数用于提取一个 每个列表元素的比较键

key specifies a function of one argument that is used to extract a comparison key from each list element

使用 lambda 表达式进行排序可以提取密钥.

Using a lambda expression, the sorting key can be extracted.

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