# Reverse Numpy array : A Step by Step Implementation #### You already know NumPy is a great python module for processing and manipulating multi-dimensional array. In this entire tutorial, you will learn how to reverse NumPy array through step by step.

There are three methods to reverse NumPy array. We will discuss all of them here.

1. Using the Shortcut or slicing method
2. Use of numpu.flip() method.
3. Using numpy.flipud()
4. Using numpu.flipr()

## Step by Step implementation to reverse Numpy array

### Step 1: Import all the necessary libraries.

Here we are using only NumPy libraries. That’s why I am importing it using the import statement.

``import numpy as np``

### Step 2:  Create NumPy array.

Now for the demonstration purpose lets we create a Numpy array. It will be of both single and multiple dimensions.

One Dimensional Array

``array_1d = np.array([10,30,40,20])``

Two Dimensional Array

``array_2d = np.array([[10,30],[60,50]])``

### Step 3:  Reverse Numpy Array.

Let’s reverse all the NumPy array I have created in step 2.

#### Method 1: Using the Shortcut.

The shortcut method to reverse the NumPy array is to use the slicing method. Use the below code.

For 1-D Array

``array_1d[::-1]``

2 -D Array

``array_2d[::-1]``

Output #### Method 2 : Use of numpy.flip() method.

The numpy.flip() accepts two arguments. One is the array you want to flip. The second the axis value 0,1 or None. It is very useful if you want to flip some specific columns or rows.

For 1-D Array

``np.flip(array_1d)``

2 -D Array

``np.flip(array_2d)``

Output #### Method 3: Using the numpy.flipud() method.

The third method for reversing the NumPy array is the numpy.flipud() method.

For 1-D Array

``np.flipud(array_1d)``

2 -D Array

To demonstrate for two-dimensional array, let’s create a diagonal matrix using the numpy.diag() method. I have not used the above 2D example here because the diagonal matrix clearly shows where the flipping has been done.

``diagonal_matrix = np.diag([10,20,30])``

Now pass it inside the np.flipud() method as an argument. It will Flip an array vertically (axis=0).

``np.flipud(diagonal_matrix)``

You will get the following output. #### Method 4: Using the numpy.flipur() method.

Now the last method to reverse the NumPy array is the numpy.fliplr() method. It will Flip an array horizontally (axis=1).  There is only one condition for using it. The NumPy array should be a 2 or N-dimensional array. I am using the same diagonal matrix used in method 3.

Execute the following line of code.

``np.fliplr(diagonal_matrix)``

Output ## Conclusion

These are the methods for reversing the NumPy array. Methods 1,2 and 3 works on both single and multi-dimensional array. But the last method 4 works on only multi-dimensional array.

Source of tutorial

Numpy Documentation 