How to swap columns of a given NumPy array?

In this article, let’s discuss how to swap columns of a given NumPy array.

Approach :

• Import NumPy module
• Create a NumPy array
• Swap the column with Index
• Print the Final array

Example 1: Swapping the column of an array. 

Python3

# importing Module
import numpy as np


# creating array with shape(4,3)
my_array = np.arange(12).reshape(4, 3)
print("Original array:")
print(my_array)

# swapping the column with index of
# original array
my_array[:, [2, 0]] = my_array[:, [0, 2]]
print("After swapping arrays the last column and first column:")
print(my_array)

Output :

Original array:
[[ 0  1  2]
 [ 3  4  5]
 [ 6  7  8]
 [ 9 10 11]]
After swapping arrays the last column and first column:
[[ 2  1  0]
 [ 5  4  3]
 [ 8  7  6]
 [11 10  9]]

Example 2: Swapping the column of an array with the user chooses.

Python3

# Importing Module
import numpy as np


# Creating array
my_array = np.arange(12).reshape(4, 3)
print("Original Array : ")
print(my_array)
# creating function for swap

def Swap(arr, start_index, last_index):
    arr[:, [start_index, last_index]] = arr[:, [last_index, start_index]]

# passing parameter into the function
Swap(my_array, 0, 1)
print(" After Swapping :")
print(my_array)

Output :

Original Array : 
[[ 0  1  2]
 [ 3  4  5]
 [ 6  7  8]
 [ 9 10 11]]
 After Swapping :
[[ 1  0  2]
 [ 4  3  5]
 [ 7  6  8]
 [10  9 11]]