Python Sort Multidimensional List first element Based on second element that already sorted

Question

I have a multidimensional List like this (the second element already sorted)

    [[92, 25], [93, 25], [95, 27], [94, 27], [94, 27], [92, 27], [89, 27], [89, 27], [92, 27], [91, 30], [90, 30], [90, 30], [90, 30], [91, 30]]

So i want to sort the first element base on the second element (Descending). Expected Output:

    [[93, 25], [92, 25], [95, 27], [94, 27], [94, 27], [92, 27], [92, 27], [89, 27], [89, 27], [91, 30], [91, 30], [90, 30], [90, 30], [90, 30]]

Right, so what went wrong with what you found about sorting by multiple items in sublists? — roganjosh, Oct 22 '19 at 18:00
Can you explain *why* this is the expected output? And what have you tried to solve this problem? — Scott Hunter, Oct 22 '19 at 18:01
Also note that you're calling this an "array" but it isn't in Python, it's a list. 99% of the the time, "array" refers to NumPy array. There is also a Python array but it's barely ever used. — roganjosh, Oct 22 '19 at 18:03
Aw i think i just solved my own problem by search at stackoverflow with your keyword mates @roganjosh i found itemgetter and it solved my own question like with 3 repeat lines — Wailan Tirajoh, Oct 22 '19 at 18:11

score 1 · Answer 1 · answered Oct 22 '19 at 18:09

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If you want to do in place sort than

arr.sort(key=lambda x:(x[1], -x[0])

otherwise can use sorted

sortedArray = sorted(arr, key=lambda x: (x[1], -x[0]))

answered Oct 22 '19 at 18:09

PraveenB

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Oops saw @roganjosh 's duplicate and definitely its a duplicate item – PraveenB Oct 22 '19 at 18:10

score 0 · Accepted Answer · answered Oct 22 '19 at 18:02

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Let me get this straight, you want a list to be sorted first based on the second element in a tuple in ascending order, and break any ties by the first element in descending order?

You can do that with sorted(l, key=lambda x: (x[1], -x[0])), assuming your elements are numbers. If not you have to write a more complex comparison function.

answered Oct 22 '19 at 18:02

orlp

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Cool, so your answer is just the same as my suggested dupe, which you could have hammered with – roganjosh Oct 22 '19 at 18:04
@roganjosh That "dupe" does not involve different orderings (ascending/descending) for different columns of the data. – orlp Oct 22 '19 at 18:05
Mmm, yes it does. But ok. – roganjosh Oct 22 '19 at 18:08
@roganjosh Where does it say that? – orlp Oct 22 '19 at 18:09
In the comments under [this](https://stackoverflow.com/a/4233482/4799172) which lead to another dupe target – roganjosh Oct 22 '19 at 18:12
@roganjosh So I was supposed to approve your suggestion of a duplicate because that question contained an answer which had a comment which linked to a relevant question? Ok. – orlp Oct 22 '19 at 18:14

Python Sort Multidimensional List first element Based on second element that already sorted

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