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# Numpy recarray.nonzero() function | Python

• Last Updated : 27 Sep, 2019

In numpy, arrays may have a data-types containing fields, analogous to columns in a spreadsheet. An example is `[(a, int), (b, float)]`, where each entry in the array is a pair of (int, float). Normally, these attributes are accessed using dictionary lookups such as `arr['a'] and arr['b']`. Record arrays allow the fields to be accessed as members of the array, using `arr.a and arr.b`.

`numpy.recarray.nonzero()` function is used to get the indices of the elements that are non-zero in the record array. It returns a tuple of arrays, one for each dimension of arr, containing the indices of the non-zero elements in that dimension.

Syntax : `numpy.recarray.nonzero()`

Parameters: None

Return : [tuple_of_arrays] Indices of elements that are non-zero.

Code #1 :

 `# Python program explaining``# numpy.recarray.nonzero() method `` ` `# importing numpy as geek``import` `numpy as geek`` ` `# creating input array with 2 different field ``in_arr ``=` `geek.array([[(``0.0``, ``2``), (``3.0``, ``-``4``), (``0.0``, ``9``)],``                     ``[(``9.0``, ``1``), (``5.0``, ``0``), (``-``12.0``, ``-``7``)]],``                     ``dtype ``=``[(``'a'``, ``float``), (``'b'``, ``int``)])`` ` `print` `(``"Input array : "``, in_arr)`` ` `# convert it to a record array,``# using arr.view(np.recarray)``rec_arr ``=` `in_arr.view(geek.recarray)``print``(``"Record array of float: "``, rec_arr.a)``print``(``"Record array of int: "``, rec_arr.b)`` ` `# applying recarray.nonzero methods``# to float record array ``out_arr ``=` `rec_arr.a.nonzero()``print` `(``"Indices of non zero elements : "``, out_arr) `` ` `# applying recarray.nonzero methods ``# to int record array``out_arr ``=` `rec_arr.b.nonzero()``print` `(``"Indices of non zero elements : "``, out_arr) `
Output:

Input array : [[( 0., 2) ( 3., -4) ( 0., 9)]
[( 9., 1) ( 5., 0) (-12., -7)]]
Record array of float: [[ 0. 3. 0.]
[ 9. 5. -12.]]
Record array of int: [[ 2 -4 9]
[ 1 0 -7]]
Indices of non zero elements : (array([0, 1, 1, 1], dtype=int64), array([1, 0, 1, 2], dtype=int64))
Indices of non zero elements : (array([0, 0, 0, 1, 1], dtype=int64), array([0, 1, 2, 0, 2], dtype=int64))

Code #2 :

We are applying `numpy.recarray.nonzero()` to whole record array.

 `# Python program explaining``# numpy.recarray.nonzero() method `` ` `# importing numpy as geek``import` `numpy as geek`` ` `# creating input array with 2 different field ``in_arr ``=` `geek.array([[(``5.0``, ``2``), (``3.0``, ``4``), (``6.0``, ``-``7``)],``                     ``[(``9.0``, ``1``), (``6.0``, ``4``), (``-``2.0``, ``-``7``)]],``                     ``dtype ``=``[(``'a'``, ``float``), (``'b'``, ``int``)])`` ` `print` `(``"Input array : "``, in_arr)`` ` `# convert it to a record array, ``# using arr.view(np.recarray)``rec_arr ``=` `in_arr.view(geek.recarray)`` ` `# applying recarray.nonzero methods to record array``out_arr ``=` `rec_arr.nonzero()`` ` `print` `(``"Output array : "``, out_arr)`
Output:

Input array : [[( 5., 2) ( 3., 4) ( 6., -7)]
[( 9., 1) ( 6., 4) (-2., -7)]]
Output array : (array([0, 0, 0, 1, 1, 1], dtype=int64), array([0, 1, 2, 0, 1, 2], dtype=int64))

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