Note: Depending on where you are in the curriculum and when you started the program, you may already have installed pyenv, Python, and pipenv. If so, you are free to skip this lesson. Before continuing, however, we recommend that you verify that everything is set up correctly by completing the steps in the "Verify and Troubleshoot your WLS2 Environment Setup" lesson.

Important: We do not install Python using the installer from python.org in our curriculum. If you have installed Python using this tool, you should uninstall it before installing this version of Python.

Currently the curriculum for this course is compatible with Python 3.8.

Before installing Python, we need to install the Python version manager pyenv. This is similar to the nvm tool we used to install Node.JS, except it controls which versions of Python we use on our system.

To install pyenv, we use the pyenv-installer.

Per the instructions on the pyenv-installer website, we start by running the following command:

$ curl https://pyenv.run | bash

Unlike nvm, pyenv does not automatically add its startup lines to your shell startup file.

The files that you have to change will depend on which shell you are running (you can check which shell you have by running echo $SHELL). Follow the instructions to update the startup files associated with the shell that you are running.

Open your .zshrc or .bashrc file with the following command:

$ code ~/.zshrc

or

$ code ~/.bashrc

Add the following lines:

export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init --path)"

To get your startup file to execute, restart your terminal.

For Windows and Ubuntu users you will need to install some extra dependencies for Python. (See here for more information about the prerequisites: pyenv Prerequisites)

First run this command to update your apt repositories:

$ sudo apt update

Next, run this command to install the packages listed on the pyenv:

$ sudo apt-get install -y build-essential libssl-dev zlib1g-dev libbz2-dev \
libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
xz-utils tk-dev libffi-dev liblzma-dev python3-openssl git

Run the following command to install Python (you'll notice pyenv makes us put in the exact version instead of being able to just say 3.8 or 3):

$ pyenv install 3.8.13

After some time this should complete without any errors. It could take a while since you are compiling Python from source code.

Once this is finished we also need to tell pyenv this is our default version of Python using this command:

$ pyenv global 3.8.13

Ensure that these changes take effect by closing your terminal and opening a new one.

You can verify that you have the correct version of Python installed by typing:

$ python --version
$ python3 --version

Both of these commands should show 3.8.13

Another piece of software we will use in class is Pipenv. We will learn more about what Pipenv is later; for now, go ahead and install it:

$ pip install pipenv

After you have installed pipenv, modify your shell startup file (either ~/.bashrc or ~/.zshrc) to add an export line. This should go somewhere after the eval "$(pyenv init --path)":

$ export PIPENV_VENV_IN_PROJECT=1

Congratulations! If you've completed all these steps you are ready to code in Python!