How to use a Python application on cPanel hosting

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The Python ecosystem with our cPanel packages

Python is a very popular computer programming language and is now one of the languages used to create and deploy websites and online applications.

The cPanel web hosting packages from LWS support the use of Python in the shared web hosting environment. You can select the Python version of your choice and integrate it into the existing web service using Phusion Passenger and WSGI interfaces.

What is Phusion Passenger?

To provide our customers with a stable, robust and secure environment, we integrate your Python applications with the Apache web service using the Phusion Passenger tool.

We do not set up a reverse proxy, and Python applications cannot run standalone on their own web server. Your Python application will not listen on any port, it will communicate exclusively in WSGI with the Passenger service. If you use a framework, find out whether it is compatible with Phusion Passenger and WSGI interfaces.

How do I install an application written in Python?

From your cPanel control panel, find the Setup Python App icon in the Software section.

On the page that follows, click on the ' Create Application ' button to add a new application.

Then fill in the fields according to your application's requirements:

• Python version: This option lets you select a specific Python version for your application.
• Application root : the location of your Python application, relative to your FTP root. We recommend that you do not put your Python application in the public_html folder.
• Application URL: the root URL of your Python application.
• Application startup file : the .py file containing the initialisation of your WSGI object (relative path to application root).
• Application Entry point : the name of your WSGI object in the file defined in Application startup file.

Then click on the " Create " button once your application has been set up.

If your application startup file does not yet exist, the tool will immediately create this file with sample content. This example will display " It works! " on all HTTP requests associated with it.

Here are the contents of this example script :

import os import sys sys.path.insert(0, os.path.dirname(__file__)) def application(environ, start_response): start_response('200 OK', [('Content-Type', 'text/plain')]) message = 'It works!\version = 'Python %s\n' % sys.version.split()[0] response = '\n'.join([message, version]) return [response.encode()]

Accessing your application from the terminal

Using the terminal on the command line is an integral part of the Python ecosystem. To access your application's environment from the terminal, connect to it (from the cPanel web terminal or from an SSH client) and copy the command shown to enter your application's environment:

This action will automatically activate the correct virtual environment for your application, including the correct version of Python and PIP, as well as any dependencies installed in the environment.

Exclude a folder/subdomain from the Python processor

Note that if your Python application is in your public_html folder, then all subfolders will be covered by the application. This behaviour can be modified, especially if you have, for example, a subfolder in your public_html attached to another domain name or subdomain.

To do this, add the following to the .htaccess file for the folder you don't want your Python application to run in:

PassengerEnabled off

This will then disable Phusion Passenger which is the connector between your Python application and your web server. Note that this will also affect all subfolders.

Debugging a Python application

To debug a Python application, you can consult the Apache error log. The Apache error log file contains :

• STDOUT and STDERR output from the Python application
• Passenger errors
• Apache errors

If you have manually set the PassengerLogFile value in your site's .htaccess file, the STDOUT and STDERR output and Passenger-related errors are sent to this file instead of the Apache log file.

You can also set the PassengerFriendlyErrorPages value to on in your .htaccess file to display errors relating to the start-up of your Python application directly on the web browser.