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Build a Code Image Generator with Flask, Pygments, and Playwright

Follow the step-by-step instructions on Real Python.

Setup

You can run the provided example project on your local machine by following the steps outlined below.

Create a new virtual environment:

python3 -m venv venv/

Activate the virtual environment:

source ./venv/bin/activate

Navigate to the folder for the step that you're currently on.

Install the dependencies for this project if you haven't installed them yet:

(venv) $ python -m pip install -r requirements.txt

Next, you need to install Playwright:

(venv) $  playwright install

Finally, run the Flask development server

(venv) $ python -m flask run

Now you can navigate to the address that's shown in the output when you start the server. Commonly, that's http://localhost:5000/.

Secret Key

If you want to deploy your Flask app later, then it's a good idea to generate a proper secret key.

If you need to create cryptographically sound data like a Flask secret key, then you can use Python's secrets module:

>>> import secrets
>>> secrets.token_hex()
'2e9ac41b1e0b66a8d93d66400e2300c4b4c2953f'

The .token_hex() method returns a hexadecimal string containing random numbers and letters from 0 to 9 and a to f. Use the value that secrets.token_hex() outputs for you and add it to your Flask project's app.py file:

# app.py

from flask import Flask, render_template

app = Flask(__name__)
app.secret_key = "2e9ac41b1e0b66a8d93d66400e2300c4b4c2953f"

# ...

To avoid saving the secret key directly in your code, it may be a good idea to work with environment variables. You can learn more about that in the Flask documentation on configuration handling.