Update for Raspberry Pi OS Bookworm

With the release of Raspberry Pi OS Bookworm, the default Python version is now Python 3.11 and a virtual environment is required to install Python packages. If you try to install something outside of a virtual environment you will be met with the following error message:

pip install streamlit

error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.

This means that you must now install virtualenv with:

sudo apt install python3-virtualenv

After installing virtualenv, you can create a virtual environment and install streamlit with:

virtualenv test
source test/bin/activate
pip install streamlit

You can also deactivate an environment with:

deactivate

Original Post

A Python virtual environment allows you to build individual environments for your programming projects to install the required packages for the projects. Keeping environments separate for each project allows for the minimal dependencies to be installed to run the project. It also prevents package versions from clashing across projects. Finally, it makes it a little bit easier to share the environment requirements with someone else who wants to run your Python project.

You can easily install virtualenv on a Raspberry Pi with pip using the following command:

pip install virtualenv

If you do not have pip installed yet, you can install it with:

sudo apt install python3-pip

To put the virtualenv bin folder on your path you can modify the ~/.bashrc file and add the following line:

export PATH=$PATH:/home/pi/.local/bin

You will need to logout and log back in for the path modification to take place. Finally, you can setup and activate a virtualenv with:

virtualenv test
source test/bin/activate

You can also deactivate an environment with:

deactivate

I hope this helps someone get started with Python and virtualenv on a Raspberry Pi!