切片具有不同长度的子列表 [英] Slicing sublists with different lengths

问题描述

我有一个清单清单.每个子列表的长度在1到100之间.每个子列表在一组数据中的不同时间包含一个粒子ID.我想在给定的时间形成所有粒子ID的列表.为此，我可以使用类似的东西:

I have a list of lists. Each sublist has a length that varies between 1 and 100. Each sublist contains a particle ID at different times in a set of data. I would like to form lists of all particle IDs at a given time. To do this I could use something like:

    list = [[1,2,3,4,5],[2,6,7,8],[1,3,6,7,8]]
    list2 = [item[0] for item in list]

list2将包含列表中每个子列表的首个元素.我不仅要对第一个元素执行此操作，还要对1到100之间的每个元素执行此操作.我的问题是，每个子列表都不存在元素号100(或66或77或其他).

list2 would contain the first elements of each sublist in list. I would like to do this operation not just for the first element, but for every element between 1 and 100. My problem is that element number 100 (or 66 or 77 or whatever) does not exists for every sublist.

是否存在创建列表列表的方法，其中每个子列表都是给定时间所有粒子ID的列表.

Is there some way of creating a lists of lists, where each sublist is the list of all particle IDs at a given time.

我已经考虑过尝试使用numpy数组来解决此问题，好像列表的长度都一样，这将是微不足道的.我尝试将-1加到每个列表的末尾以使它们的长度相同，然后掩盖负数，但是到目前为止，这对我没有用.我将在给定的时间使用ID列表来切片另一个单独的数组:

I have thought about trying to use numpy arrays to solve this problem, as if the lists were all the same length this would be trivial. I have tried adding -1's to the end of each list to make them all the same length, and then masking the negative numbers, but this hasn't worked for me so far. I will use the list of IDs at a given time to slice another separate array:

    pos = pos[satIDs]

推荐答案

lst = [[1,2,3,4,5],[2,6,7,8],[1,3,6,7,8]]
func =  lambda x: [line[x] for line in lst if len(line) > x]

func(3)
[4, 8, 7]
func(4)
[5, 8]

-更新-

func =  lambda x: [ (line[x],i) for i,line in enumerate(lst) if len(line) > x]
func(4)
[(5, 0), (8, 2)]

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