Python: Sort 2d ndarray and return a list of index in tuples

Question

I try iterate over values of a 2d ndarray and get the index as well. Therefor I tried to sort the 2d ndarray. Also tried different things with (arg-)sorting parameters of numpy.

import numpy
arr = numpy.array([[2,11,4], [33,9,5], [3,21,123]])
print(arr.argsort(axis=None)

This returns:

array([0, 6, 2, 5, 4, 1, 7, 3, 8])

But I want to return a list like this where each list element contains the 2-dimensional index like this:

[(0,0), (2,0), (0,2), (1,2), (1,1), (0,1), (2,1), (1,0), (2,2)]

v0rtex20k · Accepted Answer · 2021-03-12 21:00:48Z

2

Using numpy's unravel_index, we can do the following:

import numpy as np
arr = np.array([[2,11,4], [33,9,5], [3,21,123]])
ix, jx = np.unravel_index(arr.argsort(axis=None), arr.shape)
print(list(zip(ix,jx)))

Which outputs

[(0, 0), (2, 0), (0, 2), (1, 2), (1, 1), (0, 1), (2, 1), (1, 0), (2, 2)]

for this example, as requested.

answered Mar 12, 2021 at 21:00

v0rtex20k

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1 Comment

programmar Over a year ago

Works perfectly for me

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