# Numpy recarray.trace() function | Python

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.trace() ` function is used to return the sum along diagonals of the array.

Syntax : `numpy.recarray.trace(offset=0, axis1=0, axis2=1, dtype=None, out=None)`

Parameters:
offset : [int, optional] Offset of the diagonal from the main diagonal. Can be both positive and negative. Defaults to 0.
axis1 : [int, optional] Axes to be used as the first and second axis of the 2-D sub-arrays from which the diagonals should be taken.
axis2 : [int, optional] Axes to be used as the first and second axis of the 2-D sub-arrays from which the diagonals should be taken.
dtype : [optional] Determines the data-type of the returned array.
out : [ndarray, optional] A location into which the result is stored.
-> If provided, it must have a shape that the inputs broadcast to.
-> If not provided or None, a freshly-allocated array is returned.

Return : [ndarray] sum of a diagonal elements of the record array.

Code #1 :

 `# Python program explaining ` `# numpy.recarray.trace() 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``, ``9``)], ` `                     ``[(``9.0``, ``1``), (``5.0``, ``4``), (``-``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.trace methods ` `# to float record array  ` `out_arr ``=` `rec_arr.a.trace() ` `print` `(``"Output float traced array : "``, out_arr)  ` ` `  `# applying recarray.trace methods  ` `# to int record array ` `out_arr ``=` `rec_arr.b.trace() ` `print` `(``"Output int traced array : "``, out_arr)  `

Output:

```Input array :  [[(  5.,  2) (  3., -4) (  6.,  9)]
[(  9.,  1) (  5.,  4) (-12., -7)]]
Record array of float:  [[  5.   3.   6.]
[  9.   5. -12.]]
Record array of int:  [[ 2 -4  9]
[ 1  4 -7]]
Output float traced array :  10.0
Output int traced array :  6
```
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