Create a Minimal Web Application with Nginx, Python, Flask & Raspberry Pi

SSH into the Pi

ssh pi@raspberry

Install system dependancies

sudo apt install update
sudo apt install python3-venv  -y

Designate app folder

cd ~/
mkdir app
cd app

Create a Python Virtual Environment

python3 -m venv .

Activate the Python Virtual Environment

source bin/activate

Denote the Python being used (in the virtual environment)

which python

Install our Python Web Application Framework (Flask) using Pip (in the virtual environment)

pip install flask

Create our “Server” with server.py

Note that server.py is a name I made up for this app. You can call it welcome.py or whatever you like; server.py makes sense for this app and for future devs to use it.

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=8123)

Note the values for host and port in this example. host="0.0.0.0" and port=8123. We need these for later.

Run our Python Web application

/home/pi/app/bin/python /home/pi/app/server.py

• pi is my user
• /home/pi is my users’ root. (A shortcut to this path is cd ~/)
• /home/pi/app/bin/python is what which python gave us from above
• /home/pi/app/server.py is the absolute to my server.py file I made above.

Create a custom nginx config

/home/pi/app/nginx.conf

upstream flaskapp {
    server localhost:8123;
}

server {
        listen 80 default_server;
        listen [::]:80 default_server;

        root /var/www/html;
        index index.html index.htm index.nginx-debian.html;
        location / {
                proxy_pass http://flaskapp;
                proxy_redirect off;
        }

}

• the upstream flaskapp name is used 2 times and is arbitary
• server localhost:8123; references the host and port values from the Flask app above.
• "0.0.0.0" is localhost
• proxy_pass references the upstream name and not the localhost.

Replace default nginx configuration

sudo cp /home/pi/app/nginx.conf /etc/nginx/sites-enabled/default

• /etc/nginx/sites-enabled/default is linked to /etc/nginx/sites-available/default (so you can recover if you need)

Reload Nginx

sudo systemctl reload nginx

Run Flask Application Server

/home/pi/app/bin/python /home/pi/app/server.py

This value is discussed above.

Open your browser!

If you open your browser at http://raspberrypi you should see the Flask application data.