Python sorting arrays by element contained?

Question

I'm looking to take a list of lists and sort them by an element contained in the contained lists. For clarification, I want to have a list like this code

myList = []
myList.append([1, 2, 3])
myList.append([1, 1, 1])
myList.append([1, 3, 2])

and then sort the elements of list by the last element of each contained list and it would end up looking like this

           |
myList = ( v
    [1, 2, 3],
    [1, 3, 2],
    [1, 1, 1])

I also have the numpy library imported in this project. I was looking at argsort for numpy but I don't think you can sort it along an axis of an element

Don't use list as a variable name because it's built into python. — BallpointBen
– BallpointBen, Commented Nov 15, 2019 at 4:09
Does this need to be time and space efficient or are there not many items in this list? — Mike
– Mike, Commented Nov 15, 2019 at 4:10
Possible duplicate of Sorting list of lists by the first element of each sub-list — pyeR_biz
– pyeR_biz, Commented Nov 15, 2019 at 4:18

ExplodingGayFish · Accepted Answer · 2019-11-15 04:14:20Z

2

First of all don't use list as variable name as it is one of python built-in function, and second you can use sorted function to sort by position

l = []
l.append([1, 2, 3])
l.append([1, 1, 1])
l.append([1, 3, 2])
sorted(l,key = lambda x : x[2])
#[[1, 1, 1], [1, 3, 2], [1, 2, 3]]

answered Nov 15, 2019 at 4:14

ExplodingGayFish

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3 Comments

JohnMadden Over a year ago

I didn't know about this. Thanks, exactly what I was looking for.

pyeR_biz Over a year ago

lambda x : x[-1] will be more general to pick last element

RootTwo Over a year ago

l (el) isn't a good variable name. It looks like a '1' (one) in many fonts. Can use the operator library: my_list.sort(key=operator.itemgetter(-1))

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