Installing a Virtual Environment and python-thunderborg

Installing a Virtual Python Environment

Why a Virtual Environment

Python virtual environments are used regularly by seasoned Python programmers however, beginners may not know about this feature rich tool. Virtualenv is a tool which allows the creation of isolated python environments. So what do we get from isolated environments? Lets say you are developing a project that needs version 1 of some library. You install it globally on the RPI. A while later you start work on another project that requires the same library, but version 2. If you install version 2 globally, as you did before, it will invalidate the first project you were working on. This is where virtual environments comes to the rescue, every project is in it’s own isolated environment and you no longer need to install python packages as sudo (root) user. Which means the other advantage of virtual environments is that it’s installed in your user account not in the root of the system.

Although this API will work with Python version 2.7.x I strongly recommend writing any new code using Python 3.8 or higher. The Python 2.x versions ware at their end of life on January 1st 2020.

Building a Development Environment for your Projects

First you will need to log into your Raspberry Pi with ssh. There are many good tutorials online that explain how to do this.

As the pi user (on the newer RPI OS you’ll need to create your own user account) on your Raspberry Pi you will need to install a few system packages. I’m assuming you have installed Raspian bullseye. Python 2 is no longer installed on bullseye.

Change the below packages to the Python 2.x versions where appropriate.

$ sudo apt install build-essential python3-dev python3-setuptool \
                   git libssh-dev libffi-dev rustc-mozilla cargo-mozilla

If you’ll be using pygame instead of approxeng you’ll also need to install the following packages.

$ sudo apt install python3-dev python3-setuptools python3-numpy \
                   python3-opengl ffmpeg libsdl2-image-2.0-0 \
                   libsdl2-mixer-2.0-0 libsdl2-ttf-2.0-0 libsdl2-dev \
                   libsdl2-mixer-dev libsmpeg-dev libportmidi-dev \
                   libswscale-dev libportmidi-dev libswscale-dev \
                   libavformat-dev libavcodec-dev libtiff5-dev libx11-6 \
                   libx11-dev fluid-soundfont-gm timgm6mb-soundfont \
                   xfonts-base xfonts-100dpi xfonts-75dpi xfonts-cyrillic \
                   fontconfig fonts-freefont-ttf

Install the Python virtual environment. The pip utility can be used to install packages for either python2 or python3 there is no need to install pip for both python versions. This is also true for the virtual environment package which can create virtual environments for either version of Python. The virtualenvwrapper package is a wrapper around virtualenv that provides easy to use tools for virtualenv and will install virtualenv for you.

Note

A directory is created in the user’s home directory named .virtualenvs. In there you’ll be able to find all your project requirements and the packages you have installed for each of them.

$ sudo easy_install3 pip
# Newer systems no longer have ``easy_install`` for Python 3
# installed, however, I have found the command below to work.
$ sudo python3 /usr/lib/python3/dist-packages/setuptools/command/easy_install.py pip
$ sudo -H pip3 install virtualenvwrapper

Configure .bashrc in the pi user directory to auto load the virtualenvwrapper package.

$ nano .bashrc

Then add the following lines to the bottom of the .bashrc file.

# Setup the Python virtual environment.
VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
source /usr/local/bin/virtualenvwrapper.sh

$ . .bashrc

Create a VE (Virtual Environment) for your project. The VE name can be whatever you want and does not need to match the actual project’s name, but it might be a good idea to keep it short so that you can remember it.

$ cd /path/to/your_project
$ mkvirtualenv your_project # mkvirtualenv -p python2 your_project

After the initial creation of the VE you can use these commands to activate and deactivate a VE.

$ workon <your_project>
$ deactivate

Next you will need to install all the Python packages that your project depends on. Many of them will be in the pip repository at PyPi Repository.

Installing python-thunderborg

To install python-thunderborg in your virtual environment enter the following on the command line. Be sure your virtual environment is activated before doing this.

$ pip install python-thunderborg
or
$ pip install git+https://github.com/cnobile2012/python-thunderborg.git

If you are working on python-thunderborg itself, then python-thunderborg is the project you are working on and you’ll need to install the development.txt file mentioned below. You may want to fork my version first. This is advanced usage you and will need to have your own git account for this to work properly.

$ cd /path/to/where/your/project/will/be/rooted
$ git clone git@github.com:cnobile2012/python-thunderborg.git

If all the correct system packages have been installed you can now setup the virtual environment that python-thunderborg requires.

There are three pip files that can be used approxeng.txt, pygame.txt, or development.txt. Unless you will be mofiying the python-thunderborg code itself you will not need the development.txt file. I recommend installing ipython, it has a much better command line interface than the one you get from Python itself. The development.txt does this for you.

$ workon <your_project>
$ pip install -r requirements/approxeng.txt
$ pip install ipython # If needed, it's included in development.txt.

That should be it. If you have any issues please check all the instructions before contacting me.

Example of Setting up an App to Run at Boot

This is just an example of how to start an app on reboot my actual code below will probably not work on your system.

Setup a Cron Job

Run the crontab app.

$ crontab -e

Then add the line below to your user cron file. Remember to change the <username> to your username.

@reboot /home/<username>/bin/start_mborg_approxeng.sh

Copy the start_mborg_approxeng.sh script.

$ cd # Make sure you're in your home directory.
$ mkdir bin
$ cd /path/to/python-thunderborg
$ cd scripts/start_mborg_approxeng.sh ~/bin/