Numpy recarray.dot() 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.dot() function returns product of two record arrays.

Syntax : numpy.recarray.dot(arr, out=None) Parameters: arr : Second record 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 : A new array holding the result is returned unless out is specified, in which case it is returned. Code #1 :

Python3

# Python program explaining
# numpy.recarray.dot() method 

# importing numpy as geek
import numpy as geek

# creating 2 input array with 2 different field 
in_arr1 = 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)])

in_arr2 = geek.array([[(2.0, 1), (4.0, -3)],
                     [(8.0, 3), (6.0, 5)],
                     [(6.0, -5), (-5.0, 4)]],
                     dtype =[('a', float), ('b', int)])

print ("1st Input array : ", in_arr1)
print ("2nd Input array : ", in_arr2)

# convert it to a record array,
# using arr.view(np.recarray)
rec_arr1 = in_arr1.view(geek.recarray)
print("1st Record array of float: ", rec_arr1.a)
print("1st Record array of int: ", rec_arr1.b)
rec_arr2 = in_arr2.view(geek.recarray)
print("2nd Record array of float: ", rec_arr2.a)
print("2nd Record array of int: ", rec_arr2.b)

# applying recarray.dot methods
# between two float record array 
out_arr1 = rec_arr1.a.dot( rec_arr2.a)
print ("Output float array  : ", out_arr1) 

# applying recarray.dot methods
# between two int record array 
out_arr1 = rec_arr1.b.dot( rec_arr2.b)
print ("Output int array  : ", out_arr1)

Output:

1st Input array :  [[(  5.,  2) (  3., -4) (  6.,  9)]
 [(  9.,  1) (  5.,  4) (-12., -7)]]
2nd Input array :  [[( 2.,  1) ( 4., -3)]
 [( 8.,  3) ( 6.,  5)]
 [( 6., -5) (-5.,  4)]]
1st Record array of float:  [[  5.   3.   6.]
 [  9.   5. -12.]]
1st Record array of int:  [[ 2 -4  9]
 [ 1  4 -7]]
2nd Record array of float:  [[ 2.  4.]
 [ 8.  6.]
 [ 6. -5.]]
2nd Record array of int:  [[ 1 -3]
 [ 3  5]
 [-5  4]]
Output float array  :  [[ 70.   8.]
 [-14. 126.]]
Output int array  :  [[-55  10]
 [ 48 -11]]