numpy.flatnonzero() in Python

numpy.flatnonzero()function is used to Compute indices that are non-zero in the flattened version of arr.

Syntax : numpy.flatnonzero(arr)

Parameters :
arr : [array_like] Input array.

Return : ndarray
Output array, containing the indices of the elements of arr.ravel() that are non-zero.

Code #1 : Working

# Python program explaining
# flatnonzero() function

import numpy as geek
arr = geek.arange(-3, 4)

print ("Input  array : ", arr)

out_arr = geek.flatnonzero(arr)
print ("Indices of non zero elements : ", out_arr)

Output :

Input  array :  [-3 -2 -1  0  1  2  3]
Indices of non zero elements :  [0 1 2 4 5 6]

Code #2 : Using the indices of the non-zero elements as an index array.

# Python program using the indices of the non-zero
# elements as an index array to extract these elements

out_arr = arr.ravel()[geek.flatnonzero(arr)]

print ("Output array of non-zero number: ", out_arr)

Output :

Output array of non-zero number:  [-3 -2 -1  1  2  3]