How to deploy Python Flask apps

Did you know that Python3 is automatically packaged with Ubuntu 20.04? Let’s leverage this fact and deploy an example Flask framework application.

Step 1 - Add a NodeJS SSR app

Add a new NodeJS SSR site to your server. We’re using a NodeJS as it will install Node AND PM2 to the server. We can easily use PM2 to monitor the Flask app and keep it alive with just a few tweaks.

Step 2 - Configure app repo

In this example, we’ll use a Flask repo from XD that I modified a bit to make the port number use the one assigned by Cleavr. GitHub - armgitaar/flask-example: A minimal web app developed with Flask.

In the file, take note to the very bottom:

if __name__ == "__main__":, host="", port=os.environ.get('PORT', 5000))

Flask apps default to run on port 5000. However, the following allows the app to run on the server assigned port: port=os.environ.get('PORT', 5000).

On the repo tab, add armgitaar/flask-example to the repo and keep branch as master.

Step 3 - Configure entry and PM2 ecosystem

On the Build tab, set Entry Point to

In the PM2 ecosystem, we’ll need to set the interpreter to Python3 as well as remove a couple of configs that aren’t compatible with Python apps.

Add interpreter:

"interpreter": "/usr/bin/python3",

Remove the following lines:

 "instances": "max",
 "exec_mode": "cluster_mode",

The ecosystem should look similar to the following:

  "name": "",
  "script": "",
  "args": "",
  "log_type": "json",
  "cwd": "/home/cleavr/",
  "interpreter": "/usr/bin/python3",
  "env": {
    "PORT": assigned port number,
    "CI": 1,

Step 4 - Configure deployment hooks

On the deployment hooks page,

  • Disable Install NPM Packages hook
  • Disable Build Assets hook

Add a new hook to install Python dependencies:

pip install -r requirements.txt

Order the above hook to run before the activation deployment hook.

Step 5 - deploy!

Once all of the above is complete, deploy the app!

You should see a page that looks like the following:


AND for Django apps?