Skip to content

Pythoneo

Online How to Python stuff

How to reverse array in Numpy?

Posted on March 19, 2021March 2, 2023 By Luke K

Let’s learn how to reverse an array in the Numpy Python library. We will check a few methods and tricks.
Numpy reverse array left right direction

The easiest way to reverse an array in Numpy is just to use the flip function.

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

reversed_array = np.flip(my_array)
print(f"This is reversed array: \n{reversed_array}")

Numpy how to reverse array

The array just got reversed.

However, there are other ways to reverse an array. This is how you reverse an array in the up-down direction. There is a dedicated Numpy flipud function for that.

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

reverse_array_up_down = np.flipud(my_array)
print(f"Array reversed in up/down direction: \n{reverse_array_up_down}")

Numpy reverse array up down direction

As you can see, the array just got reversed and looks way different than the previous flip. This flipped array worked in an up/down direction, which can be useful in some use cases.

See also  How to permute in Numpy?

With this simple Python trick, there is also the possibility to do the same without flipud.

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

flipped_array = my_array[::-1]
print(f"Array reversed in up/down direction without Numpy function: \n{flipped_array}")

Python reverse array up down direction

As you can see, the result is the same. my_array [::-1] simply created an array view in the up-down direction, as expected.

See also  How to convert Numpy array to Python list?

The same is possible in the left-to-right direction, of course. Fliplr is the name of a Numpy function.

import numpy as np

my_array = np.array([[11, 12, 13],
                    [21, 22, 23],
                    [31, 32, 33]])
print(f"This is my array: \n{my_array}")

flipped_array = np.fliplr(my_array)
print(f"Array reversed in left/right direction:  \n{flipped_array}")

Numpy reverse array left right direction

The array was flipped from left to right.

Knowing all of these methods, you can flip arrays according to your needs.

See also  How to save array as csv file with Numpy?
numpy, Python Tags:array, flip, reverse

Post navigation

Previous Post: How to convert Numpy array to Python list?
Next Post: Ways how to convert numpy array to string

Categories

  • bokeh (1)
  • datetime (3)
  • Django (5)
  • glob (1)
  • io (1)
  • json (1)
  • math (5)
  • matplotlib (10)
  • numpy (95)
  • OpenCV (1)
  • os (3)
  • Pandas (2)
  • paramiko (1)
  • pathlib (2)
  • Pillow (3)
  • Plotly (3)
  • Python (29)
  • random (7)
  • requests (1)
  • Scipy (4)
  • Seaborn (7)
  • shutil (1)
  • sqlite3 (1)
  • statistics (16)
  • sys (1)
  • Tkinter (9)
  • turtle (2)
  • Uncategorized (1)
  • urllib (1)
  • webbrowser (1)

RSS RSS

  • How to create violin plot using seaborn?
  • How To Use Colormaps In Matplotlib?
  • How to calculate bonds in Python
  • How to handle trigonometry in Python
  • How to Convert Int to Binary in Python?
  • How to fix ValueError: The truth value of an array with zero elements is ambiguous?
  • How to solve NameError: name ‘numpy’ is not defined
  • How to insert seaborn lineplot?
  • How to Find the Length of an Array in Python?
  • How to reset secret key in Django

Tags

arithmetic mean array axis button calculations chart conversion copy count counter data type dictionary dimension draw error files fill float generate grid GUI image index integer list matrix max mean median min normal distribution plot random reshape rotate round size standard deviation string sum test text time variance zero

Copyright © 2023 Pythoneo.

Powered by PressBook WordPress theme

We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. By clicking “Accept”, you consent to the use of ALL the cookies.
Cookie settingsACCEPT
Manage consent

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.
Necessary
Always Enabled
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Non-necessary
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.
SAVE & ACCEPT