Finding indexes of elements in nested arrays

March 15, 2023

I have an array arr = [[[1, 2], [3, 4]], [5, 6]].

I am looking for a function f that returns me the indexes of the elements also in the nested array given only arr as input.

For example, function(arr, 2) -> (0, 0, 1)

Has some library implemented it?

Of course it’s not a problem if the array is a numpy array.

>Solution :

For this you dont necessarely need a special library, you can use the numpy where function, like this:

import numpy as np

def find_indices(arr, x):
    indices = np.where(np.array(arr) == x)
    return tuple(indices[0])

# example usage
arr = [[[1, 2], [3, 4]], [5, 6]]
print(find_indices(arr, 2))  # output: (0, 0, 1)

edit: my code seem to fail on some case with the error ValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 2 dimensions. The detected shape was (2, 2) + inhomogeneous part.

here is a version that work without numpy

def find_indices(arr, value):
    for i, sublist in enumerate(arr):
        for j, subsublist in enumerate(sublist):
            for k, item in enumerate(subsublist):
                if item == value:
                    return i, j, k
    return None

arr = [[[1, 2], [3, 4]], [5, 6]]
print(find_indices(arr, 2))  # Output: (0, 0, 1)