Switching between Python 2 and 3 versions on Ubuntu 20.04

Are you missing Python 2 on your Ubuntu 20.04 system? It was dropped out completely since this Focal Fossa release, but here is how to install it and switch between version 2 and version 3 on your current Ubuntu installation.

In the recent past, there has been a bit of debate on which Python version should one learn. Python 2 or Python 3. It’s now 2020 and pretty evident that Python 3 is the way to go. However, Python 2 is still in the market, and some people, including me, still use it in development. It brings forth the necessity of how we set up and switch between the two versions on your Linux system.

Ubuntu 18.04 LTS release came with several changes, and one is that Python 2 was no longer the default Python version in the system. Welcome, Ubuntu 20.04 LTS release; canonical dropped Python 2 entirely and no longer included it among the installation packages.

See the image below. When we try to execute the Python 2 command, which is by default “python,” we get “command not found” error.

Python 2 not installed in Ubuntu 20.04
Python 2 not packaged in Ubuntu 20.04

In this post, we will show you how to:

  • Install Python 2 in Ubuntu 20.04 LTS
  • Switch between Python 3 and Python 2 versions

Installing Python 2 in Ubuntu 20.04 LTS

Step 1) Launch the Terminal and type any of the commands below. You will be required to enter your root password.

$ sudo apt install python2
OR
$ sudo apt install python-minimal

Install Python2 in Ubuntu 20.04 LTS
Install Python2 in Ubuntu 20.04 LTS

Step 2) Once the installation complete, you can check the Python 2 version using the “–version” command.

python2 --version
python3 --version

Check the python version installed
Check the python version installed

From the image above, we can see we are running Python 2.7 and Python 3.8. Now, let’s jump on to one of the important parts of this tutorial of how to configure Python and switch between the two versions – Python 2 and Python 3.

How to switch between Python 2 and 3 versions on Ubuntu 20.04

Method 1: My recommended way by configuring

Step 1) Check all the available Python versions in your system. To do so, we will need to check the /bin directory. That is because we can have variations in Python 3. Say Python 3.7 and Python 3.8. In such situations, the –version command won’t be useful as it only lists the currently configured version.

Execute the commands below on the Terminal.

ls /usr/bin/python*

Check all the installed Python versions in the bin directory
Check all the installed Python versions in the bin directory

Step 2) Once we have listed all the versions present on the system, we need to check whether there are any Python-alternatives configured.

Execute the command below on the Terminal.

sudo update-alternatives --list python

Check for any Python alternatives configured on the system
Check for any Python alternatives configured on the system

From the image above, we see that there are no Python alternatives configured.

Step 3) Now, we will configure two Python alternatives. From the image in Step 2 above, we saw that I have Python 2.7 and Python 3.8 present on my system.

Execute the commands below on the Terminal.

$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 1
$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 2

Configure Python Alternatives
Configure Python Alternatives

Step 4) We need to confirm the Python alternatives set and whether they are in use.
Execute the command below again.

$ sudo update-alternatives --config python

Confirm the Python Alternatives set
Confirm the Python Alternatives set

On the prompt that appears on the Terminal, enter 1 or 2 to make your selection. In this post, we want to use Python 2; therefore, we will enter option 1.

Step 5) Now, let’s check the Python version currently running on our system. Execute the command below.

python --version

Check the currently running Python Version
Check the currently running Python Version

To switch to another Python version, all you need to do is execute the command on Step 4 and select the other option. In this case, we would choose option 2 to use Python 3.

Method 2: Old-school way without configuration

This other method, we would refer to it as the manual way since we won’t perform any configurations. Follow the procedure below.

Step 1) Install Python 2 with the command below.

sudo apt install python2

Step 2) Check the Python versions present in your system by running the command below.

ls /usr/bin/python*

Check all the installed Python versions in the bin directory
Check all the installed Python versions in the bin directory

Step 3) In this post, we currently have Python 2 and Python 3 available. Now write your Python 2 or Python 3 code. 

For example, below is a Python 2 code to print the sentence “Hello, This Fosslinux.com.

Python2 Code
Python2 Code

Step 4) To execute your code using Python 2, you will need to specify the version manually. For example, the python file is called Example.py. Execute the command below.

python2 Example.py

Execute the Python 2 code
Execute the Python 2 code

If we used Python 3 to execute the code below, we would get an error, as shown below.

Error when using Python3 to execute Python2 code
Error when using Python3 to execute Python2 code

If we were writing code using Python 3, we would specify Python 3 when running the program.

Conclusion

Despite Python 2 being dropped in the recent Linux releases, some people still find it advantageous and use it in their development. There are vast applications built using Python 2, and the transition to Python 3 has not been put into effect fully.

These and many other reasons make Python 2 still relevant in the development community. With the methods described above, you will be able to switch from one Python version to another easily when coding.

Arun Kumar
Arun did his bachelor in computer engineering and loves enjoying his spare time writing for FOSS Linux. He uses Fedora as the daily driver and loves tinkering with interesting distros on VirtualBox. He works during the day and reads anything tech at night. Apart from blogging, he loves swimming and playing tennis.

2 COMMENTS

  1. hello

    i’m starting with UBUNTU. i installed 20/04 LTS and get an error message when trying to install python2
    sudo apt install python2 start but
    reading > ok
    dependencies
    status information reading > ok
    impossible to find python2 paquet.

    i have a old school python script that need the 2 and not the 3 !
    i tried to upgrade it by changing the print syntax but now experiencing decode_encode issues.

    thanks for the help.

LEAVE A REPLY

Please enter your comment!
Please enter your name here

STAY CONNECTED

23,648FansLike
360FollowersFollow
16SubscribersSubscribe

LATEST ARTICLES

How to install CMake on Ubuntu

CMake is a cross-platform free and open-source software tool designed to build, test, and package the software. CMake uses a simple platform and compiler-independent configuration files to control the software compilation process.

How to install Lightworks on Ubuntu

Even though Linux may not get a native installer of video editing software like Adobe Premiere or Final Cut Pro, that doesn't mean there are no industry standards tools available. Lightworks is non-linear editing (NLE) video mastering app for Windows, Linux, and macOS. Installing it on Ubuntu is simple due to deb package availability.

How to install DaVinci Resolve on Fedora

Davinci Resolve is a professional application used for color correction, video editing, visual effects, and motion graphics. It is one of the extensively used software by movie industries located in Hollywood.

The 10 Best Programming Languages for Hacking

One of the significant entities we have in Cyber Security is Ethical Hacking (ETH). It is the process of detecting and finding flaws or vulnerabilities in a system that a hacker would exploit.

5 Ways to Open a Terminal in Ubuntu

Even though Ubuntu supports many applications with amazing Graphical User Interfaces (GUI), there are always reasons why users prefer using the Terminal to perform different tasks.

How to install Wine on Fedora Workstation

Linux distributions are becoming more and more popular every day, and Fedora Workstation is not left behind. This popularity brings forth the need to run Windows applications on Linux distros like Fedora. Windows has quite some excellent Software that is not available for Linux.

MUST READ

Linux is growing faster than ever. As per the latest report, there is a drop in the Windows 10 market share for the first time, and Linux's market share has improved to 2.87% this month. Most of the features in the list were rolled out in the Pop OS 20.04. Let's a detailed look into the new features, how to upgrade, and a ride through video.
Elementary OS 5.1 Hera has received a point release with a handful of new features and bug fixes, and we will be reviewing the significant changes in this article. For those new to elementary OS, this Ubuntu-based Linux distribution uses their inhouse built Pantheon desktop environment and AppCenter.

Linux Mint vs. Ubuntu – which is best for you?

The conundrum is that which one among them? The best solution is to try both of them out, and then choose whatever seems to work the best for your needs. But here, we're giving you some distinctions between the both that might make it easier for you to make a choice.

All about Ubuntu editions and which version should you use?

Ubuntu is one of the most popular Linux distributions developed and released by Canonical, and not without reason. It has very enriched repositories, with support for all the programs you could ever need.

10 ways to use the Chown command with examples

Any file in a Linux system belongs to a particular owner(s) and a group. It is one of the many features that maintain security in Linux systems. For example; If a file belongs to say UserA, then UserB cannot manipulate the data depending on any additional permissions set unless the user has permission to do that.

10 Best PDF Editors for Linux

In this article, we will take a look at 10 of the best PDF editors and tools out there in 2019 that are available for Linux platforms. The editors are going to be judged on the basis of their functionalities, portability, ease of installation, price, and convenience.