How to reverse column order in a matrix with Python?

In this article, we will see how to reverse the column order of a matrix in Python.

Examples:

Input: 
arr = [[10,20,30],
 [40,50,60],
 [70,80,90]]
Output:
30 20 10 
60 50 40
90 80 70 

Input:
arr = [[15,30],
 [45,60],
 [75,90],
 [105,120]]
Output:
30 15
60 45
90 75
120 105

Matrices are created in python by using nested lists/arrays. However, a more efficient way to handle arrays in python is the NumPy library. To create arrays using NumPy use this or matrix in python once go through this.

Method 1:

1. Iterate through each row
2. For every row, use list comprehension to reverse the row (i.e. a[::-1])
3. Append the reversed rows into a new matrix
4. Print the matrix

Example:

Output:

Method 2:

An array object in NumPy is called ndarray, which is created using the array() function. To reverse column order in a matrix, we make use of the numpy.fliplr() method. The method flips the entries in each row in the left/right direction. Column data is preserved but appears in a different order than before.

Syntax:  numpy.fliplr(m)

Parameters: m (array_like) - Input array must be at least 2-D.

Returned Value: ndarray - A view of m is returned with the columns reversed, and this operation's time complexity is O(1).

Example:

Output:

Flipped_arr contains a reversed column order matrix where the column order has changed from c1,c2,c3 to c3,c2,c1, and the elements of each column remain intact under their respective headers (c1,c2,c3).