How to sort list in python with different indexes based on condition?

Question

I am new in python,I want to sort a list of lists in python in non-decreasing order by the first index but if the first index holds equal values sort by the second index in decreasing order

ex [[3,3],[3,2],[1,3]]

output [[1,3],[3,3][3,2]]

ex2[[7,0],[4,4],[7,1],[5,0],[6,1],[5,2]]

output[[4, 4], [5, 2],[5, 0], [6, 1], [7, 1],[7, 0]]

in c++ I used this function as key

   static bool lessThan(vector<int> &l , vector<int> &r)
{

    if (r[0] == l[0])
        return l[1]>r[1];

        return l[0]<r[0];
}

but on python key function has different behaviour

Mark · Accepted Answer · 2020-06-08 05:16:47Z

1

Since you are just sorting numbers, you can take a shortcut and just take the negative of the second element in the tuple:

l = [[3,3],[3,2],[1,3], [3,5], [3,0], [3, -1]]

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

# [[1, 3], [3, 5], [3, 3], [3, 2], [3, 0], [3, -1]]

answered Jun 8, 2020 at 5:16

Mark

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