IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices

This error message is raised when you try to use invalid indices to access elements of a list or array in Python. The valid indices include integers, slices, ellipsis, numpy.newaxis, and boolean or integer arrays.

For example, if you have a list "my_list" and try to access an element using a string as an index:

my_list = [1, 2, 3]
print(my_list['a'])

You will get the "IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices" error message because 'a' is not a valid index.

Similarly, if you have a numpy array "my_array" and try to access an element using a float as an index:

import numpy as np

my_array = np.array([1, 2, 3])
print(my_array[1.5])

You will get the same error message because 1.5 is not a valid index.