This guide is heavily based on the one by Prof Jean Salac.

Python doesn’t allow you (anymore) to install modules globally, and so to install modules (Python libraries that don’t come with the standard installation), you need to work with a virtual environment or venv. You will need to use virtual environments periodically in this class.

This guide assumes that you’ve already finished the Getting Started Lab and therefore are working in a Unix-based system and have Python.

Setting up a new virtual environment

  1. Open a Terminal through VSCode (within WSL if you’re on Windows)
  2. Make a directory to store your virtual environments. If you use Python for other purposes, you’ll likely need different virtual environments.
mkdir -p ~/.venvs
  1. Create a virtual environment for this class in your new folder:
python3 -m venv ~/.venvs/cs257_venv

Note: You may get an error message to install the python3-venv package. If you get this message, follow the instructions in that message on how to install it in your system.

Activating a virtual environment

After the following command, you should see in your terminal that the left-hand side of each line will now have a prefix with the same name as your virtual environment:

source ~/.venvs/cs257_venv/bin/activate

Remember to deactivate when you are done:

deactivate

Installing pip

To install new modules, you’ll need the Python installer program, pip.

  1. Check if you have pip installed in your virtual environment:
pip3 --version

If you have pip already, skip to the next section.

WSL & Ubuntu

Before installing pip, you should make sure everything is up to date:

sudo apt update
sudo apt upgrade

Then install away:

sudo apt install python3-pip

macOS

You should already have pip3 since it comes with Python by default, but if you for some reason don’t, you should update first:

brew update
brew upgrade

And then install Python again:

brew install python3

Everyone

Remember to double check that pip is properly installed now:

pip3 --version

Installing modules

There are several modules you’ll likely want in this class, so we’ll aim to get them all set up here. You don’t have to install them all right away though.

Coverage

To install coverage (for tests), make sure you have activating your virtual environment and then type the following:

pip3 install coverage

If that doesn’t work, you can try:

python3 -m pip install coverage

Flask

Install Flask (for the Flask deliverable):

pip3 install Flask

psycopg2

We’ll also be using a module called psycopg2:

pip3 install psycopg2-binary