# numpy.flatnonzero() in Python

• Last Updated : 28 Nov, 2018

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

Syntax : numpy.flatnonzero(arr)

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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]
```
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