如果它的索引在另一个列表上，则从列表中获取项目

Question

Well, I was looking on the site and I didn't find anything that could help me, so I came to ask. How do I get items from a list if its index is on another list ?

Example:

I have an array of vectors:

[[0.0,0.0,0.1] [0.4,0.23,0.175] [0.0,1.,0.5] [0.0,0.03,0.1] [0.02,0.0,0.3]]

and a list of indices:

[0,2,3]

I want a result like this:

[[0.0,0.0,0.1] [0.0,1.,0.5] [0.0,0.03,0.1]]

how can I get this result? Grateful for any help :)

Answer 1

something like this

lst1 = [[0.0, 0.0, 0.1], [0.4, 0.23, 0.175], [0.0, 1., 0.5], [0.0, 0.03, 0.1], [0.02, 0.0, 0.3]]
lst2 = [0, 2, 3]
lst3 = [x for idx, x in enumerate(lst1) if idx in lst2]
print(lst3)

output

[[0.0, 0.0, 0.1], [0.0, 1.0, 0.5], [0.0, 0.03, 0.1]]

Answer 2

You can do this with a list comprehension.

For example:

mylist = [[0.0,0.0,0.1], [0.4,0.23,0.175], [0.0,1.,0.5], [0.0,0.03,0.1], [0.02,0.0,0.3]]
indices = [0,2,3]
result = [mylist[i] for i in indices]

result is now [[0.0, 0.0, 0.1], [0.0, 1.0, 0.5], [0.0, 0.03, 0.1]]