Return equivalent of `:` from function for indexing array

Question

I have a large array and a function that returns index lists into the array, i.e.,

import numpy

n = 500
a = numpy.random.rand(n)

def get_idx(k):
    # M         


        

Answer 1

NumPy has a helper np.s_[] which can be used to construct slice and Ellipsis objects:

def get_idx(k):
    return np.s_[:] if k > 6 else np.s_[:k]

    # or even np.s_[:None if k > 6 else k]

In general, a[np.s_[ ]] is exactly the same as a[ ].