Numpy recarray.swapaxes() 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.swapaxes() function return a view of the array with axis1 and axis2 interchanged.

Syntax : numpy.recarray.swapaxes(axis1, axis2)

Parameters:
axis1 : [int] First axis.
axis2 : [int] Second axis.

Return : [ndarray] Resultant array.

Code #1 :

# Python program explaining
# numpy.recarray.swapaxes() 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.swapaxes methods
# to float record array taking axis1 = 0 and axis2 = 1
out_arr = rec_arr.a.swapaxes(0, 1)
print ("Output float array : ", out_arr)

# applying recarray.swapaxes methods
# to int record array taking axis1 = 1 and axis2 = 0
out_arr = rec_arr.b.swapaxes(1, 0)
print ("Output int 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 array :  [[  5.   9.]
 [  3.   5.]
 [  6. -12.]]
Output int array :  [[ 2  1]
 [-4  4]
 [ 9 -7]]

Code #2 :

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

# Python program explaining
# numpy.recarray.swapaxes() 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.swapaxes methods to
# record array taking axis1 = 0 and axis2 = 1
out_arr = rec_arr.swapaxes(1, 0)

print ("Output record array : ", out_arr)

Output:

Input array :  [[( 5.,  2) ( 3.,  4) ( 6., -7)]
 [( 9.,  1) ( 6.,  4) (-2., -7)]]
Output record array :  [[( 5.,  2) ( 9.,  1)]
 [( 3.,  4) ( 6.,  4)]
 [( 6., -7) (-2., -7)]]