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Flask is the smallest viable WSGI app. One file imports your app object and aliases it as application. For the underlying tool, see Python.

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Before you begin

  • A Python app created in cPanel, version 3.10 or 3.11.
  • The app root contains your Flask code (e.g. app.py defining app = Flask(__name__)).
  • A requirements.txt listing Flask and your other packages.

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Wire up Passenger

1

Create passenger_wsgi.py

passenger_wsgi.py
from app import app as application
If your Flask app object is named differently (e.g. flask_app = Flask(__name__)), alias it: from app import flask_app as application.
2

Install dependencies

Click Run Pip Install in the cPanel app management page.
3

Restart

Click Restart.

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Strip the dev server

Most Flask tutorials end with: 
if __name__ == '__main__':
    app.run(debug=True)
Leave the if __name__ block, or remove it. It’s never executed under Passenger anyway. Just don’t call app.run() at module top level.

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Common issues

passenger_wsgi.py doesn’t expose application. Check the import line: from app import app as application.
Pip ran against the system Python, not the per-app virtualenv. Install via the cPanel Run Pip Install button, or activate the env first in SSH.
Passenger caches the loaded modules. Restart with the Restart button or touch tmp/restart.txt.

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Open a ticket

Best for anything that needs an account check or a config change on our end.

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