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# 2.1.1. Python

This section describes how to configure the Python environment to run experiments and develop code for the ETSI TeraFlowSDN controller. In particular, we use PyEnv to install the appropriate version of Python and manage the virtual environments.

## Upgrade the Ubuntu distribution

Skip this step if you already did it during the installation of your machine.

    sudo apt-get update -y
    sudo apt-get dist-upgrade -y

## Install PyEnv dependencies

    sudo apt-get install -y make build-essential libssl-dev zlib1g-dev libbz2-dev libreadline-dev libsqlite3-dev wget \
        curl llvm git libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev

## Install PyEnv

We recommend installing PyEnv through
PyEnv Installer. Below you can find the instructions, but we refer you to the link for updated instructions.

    curl https://pyenv.run | bash
    # When finished, edit ~/.bash_profile // ~/.profile // ~/.bashrc as the installer proposes.
    # In general, it means to append the following lines to ~/.bashrc:
    export PYENV_ROOT="$HOME/.pyenv"
    command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"
    eval "$(pyenv init -)"
    eval "$(pyenv virtualenv-init -)"

In case .bashrc is not linked properly to your profile, you may need to append the following line into your local .profile file:

    # Open ~/.profile and append this line:
    +source "$HOME"/.bashrc

## Restart the machine

Restart the machine for all the changes to take effect.

    sudo reboot

## Install Python 3.9 over PyEnv

ETSI TeraFlowSDN uses Python 3.9 by default. You should install the latest stable update of Python 3.9, i.e., avoid "-dev" versions. To find the latest version available in PyEnv, you can run the following command:

    pyenv install --list | grep " 3.9"

At the time of writing, this command will output the following list:

      3.9.0
      3.9-dev
      3.9.1
      3.9.2
      3.9.4
      3.9.5
      3.9.6
      3.9.7
      3.9.8
      3.9.9
      3.9.10
      3.9.11
      3.9.12
      3.9.13
      3.9.14
      3.9.15
      3.9.16 ** always select the latest version **

Therefore, the latest stable version is Python 3.9.16. To install this version, you should run:

    pyenv install 3.9.16
        # This command might take some minutes depending on your Internet connection speed
        # and the performance of your machine.

## Create the Virtual Environment for TeraFlowSDN

The following commands create a virtual environment named as `tfs` using Python 3.9 and associate that environment with the current folder, i.e., `~/tfs-ctrl`. That way, when you are in that folder, the associated virtual environment will be used, thus inheriting the Python interpreter, i.e., Python 3.9, and the Python packages installed on it.

    cd ~/tfs-ctrl
    pyenv virtualenv 3.9.16 tfs
    pyenv local 3.9.16/envs/tfs

After completing these commands, you should see in your prompt that now you're within the virtual environment `3.9.16/envs/tfs` on folder `~/tfs-ctrl`:

    (3.9.16/envs/tfs) tfs@tfs-vm:~/tfs-ctrl$

In case that the correct pyenv does not get automatically activated when you change to the tfs-ctrl/ folder, then execute the following command:

    cd ~/tfs-ctrl
    pyenv activate 3.9.16/envs/tfs

## Install the basic Python packages within the virtual environment

From within the `3.9.16/envs/tfs` environment on folder `~/tfs-ctrl`, run the following commands to install the basic Python packages required to work with TeraFlowSDN.

    cd ~/tfs-ctrl
    ./install_requirements.sh

Some dependencies require to re-load the session, so log-out and log-in again.

## Generate the Python code from the gRPC Proto messages and services

The components, e.g., microservices, of the TeraFlowSDN controller, in general, use a gRPC-based open API to interoperate. All the protocol definitions can be found in sub-folder `proto` within the root project folder. For additional details on gRPC, visit the official web-page gRPC.

In order to interact with the components, (re-)generate the Python code from gRPC definitions running the following command:

    cd ~/tfs-ctrl
    proto/generate_code_python.sh