Updating Python on Ubuntu 20.04 on WSL2

Ubuntu on WSL2 currently comes loaded with Python v3.8, which is the default in Ubuntu 20.04. I wanted to update to Python v3.10, as I try to use more recent software releases when starting new projects. Updating Python took more work than I thought it would (I'm more familiar with Node and utilizing node version manager to manage Node versions). Eventually I did get it all worked out, and in an effort to remember what I did, I'm writing this post to jot down the steps.^[1]

Please be aware that I'm not fully up-to-date on current Python practices. Chances are these steps may not be best methods, but it worked for me.

Steps

All instructions assume you're running them in a WSL2 terminal, not a Windows host terminal.

Quick overview:

1. Check current Python version
2. Add deadsnakes PPA and install Python 3.10
3. Update Python alias with update-alternatives
4. Install pip and other utilities

1. Check current Python version

It's always good to know what you already have so we can check by running a couple commands

python3 --version

Version 3.8.10 is the current Python version when running vanilla, up-to-date Ubuntu 20.04 in WSL2. If this returns a version greater than 3.8.10, congrats, you're done!

You can see where it's loading python3 from by

which python3

You must use python3 as the Python command, as python is not installed in Ubuntu by default.^[2]

2. Add deadsnakes PPA and install Python 3.10

The official method to install different version of Python is by downloading the source code and compiling it yourself. Rather than go through that, deadsnakes has created a PPA that contains recent versions of Python compiled for Ubuntu.

To add this PPA to your system run

sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt update

Once added, you can now install Python 3.10 by running

sudo apt install python3.10
python3.10 --version #Python 3.10.4
which python3.10 #/usr/bin/python3.10

3. Update Python alias with update-alternatives

Since you can have multiple versions of Python installed side-by-side, it's important to preface all Python commands by specifying the specific version. By default, calling python3 will use still use Python 3.8.10. If you want to use 3.10, you'll always have to call python3.10.

Notice also that calling python will still give a command not found message.

Ubuntu has a package called update-alternatives that can manage calling different versions of packages and have them share a common command. In this case, we want to be able to just use python to reference 3.10.4. You can do so by running

sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.8 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.10 2

Now when you run python --version you should get Python 3.10.4.^[3]

4. Install pip and other dependencies

To finish up, there's a few other Python tools necessary for development. You'll need pip for package management, venv for virtual environments, and a couple other tools:

sudo apt install python3-pip python3.10-pip python3.10-venv python3.10-distutils
curl -sS https://bootstrap.pypa.io/get-pip.py | python3.10
source ~/.bashrc
pip --version

4.1 Virtual Environments

I always use a virtual environment when I do any Python project. You never know if you'll need to use a package not included in the standard library. Since we just installed a compatible version of venv, we can create a virtual environment in our project's root directory and activate it by

python -m venv venv
source venv/bin/activate

I usually also make sure the latest version of pip is installed in the virtual environment and can do so by

pip install -U pip

Alternatives

There is pyenv that can perform similarly to node version manager. I did try to install this at one point a while ago, but I messed something up. I do think it'd be worthwhile to check out and try again in the future.

Final Thoughts

By no means am I a Python expert, but I wanted to jot down how I managed to update to a newer version of Python in WSL2. Hopefully these steps will at least point you in the right direction. Just to reiterate, there is most definitely a better method of doing this, but I got my system working well enough for me. If you know of a better way, drop me a line.