How To Install Python 3 Alongside Python 2.7 on Ubuntu 18.04

In this article, we will guide you through the process of installing Python 3 alongside Python 2.7 on Ubuntu 18.04. This is particularly useful for developers who need to use both versions of Python for different projects.

Checking the Existing Python Installation

Before installing Python 3, it’s important to check if it’s already installed on your system. Ubuntu 18.04 comes with Python 3.6 pre-installed. You can check this by running the following command in your terminal:

python3 --version

This command will display the version of Python 3 installed on your system. If Python 3 is already installed, you can skip the next section.

Installing Python 3

If Python 3 is not installed, you can install it by running the following command in your terminal:

sudo apt install python3

The sudo command allows you to run commands with administrative privileges. apt is the package handling utility in Ubuntu. The install command tells apt to install the specified package, in this case, Python 3.

After the installation, verify it by running python3 --version again. It should now display the version number of Python 3.

Setting Up a Virtual Environment

To avoid conflicts between Python 2.7 and Python 3, it’s recommended to set up a virtual environment for Python 3. A virtual environment is a self-contained directory tree that contains a Python installation for a particular version of Python, plus a number of additional packages.

To set up a virtual environment, first, install the venv module using the following command:

sudo apt install python3-venv

Then, create a new virtual environment by running:

python3 -m venv myenv

Replace myenv with the name you want to give to your virtual environment. The -m option tells Python to run the venv module as a script.

Activating the Virtual Environment

To start using the virtual environment, you need to activate it. Run the following command:

source myenv/bin/activate

This changes your shell’s environment variables so that running python will get you this particular version and installation of Python. You will see (myenv) in your terminal prompt, indicating that you are now working within the virtual environment.

Installing Additional Packages

Within the virtual environment, you can use pip, the Python package installer, to install additional packages. First, install pip for Python 3:

sudo apt install python3-pip

Then, you can install any package by running:

pip install packagename

Replace packagename with the name of the package you want to install.

Deactivating the Virtual Environment

When you’re done working in the virtual environment, you can deactivate it by simply running:

deactivate

This will put you back to the system’s default Python interpreter.

By following these steps, you can successfully install Python 3 alongside Python 2.7 on Ubuntu 18.04 and switch between them as needed. Remember to use python3 instead of python when you want to run Python 3 code. Happy coding!