How to Deploy a Selenium-based Flask Application on PythonAnywhere

Learn how to successfully deploy a Selenium-based Flask application on PythonAnywhere without running into compatibility issues between Chrome and ChromeDriver.
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Introduction

Deploying a web application can be challenging, especially when dealing with automated tasks using tools like Selenium. Many developers face issues related to browser and driver compatibility, particularly when moving from a local environment to a cloud platform. In this guide, we will tackle a common problem: how to deploy a Selenium-based Flask application on PythonAnywhere while avoiding common pitfalls such as session creation errors.

The Problem: Compatibility Issues

When trying to run a Selenium automated task via a Flask application on PythonAnywhere, users often encounter errors like:

[[See Video to Reveal this Text or Code Snippet]]

This error indicates that there's a mismatch between the installed version of ChromeDriver and the Chrome browser version present on the server.

Initial Attempts to Solve the Issue

In an attempt to solve this issue, the developer tried using webdriver-manager to automatically update the ChromeDriver:

[[See Video to Reveal this Text or Code Snippet]]

However, this resulted in another error:

[[See Video to Reveal this Text or Code Snippet]]

This cycle of errors can be frustrating and confusing.

The Solution: Use Default ChromeDriver and Chrome

Instead of utilizing webdriver-manager, the recommended approach on PythonAnywhere is to use the default ChromeDriver and Chrome that are already installed. This will minimize compatibility issues and simplify the deployment process.

Steps to Follow

Check the Default Versions: First, confirm the versions of Chrome and ChromeDriver present on PythonAnywhere. You can usually find this information in the PythonAnywhere documentation or by running commands in a Bash console.

Using Default ChromeDriver:

Simply initialize the Selenium WebDriver without trying to manage the ChromeDriver using webdriver-manager.

Use the following code in your Flask application:

[[See Video to Reveal this Text or Code Snippet]]

This code ensures you are using the versions already provided by PythonAnywhere.

Testing Your Application: After updating your Flask app to use the default ChromeDriver, test the application thoroughly to ensure that Selenium functions as expected via the POST request.

Deployment: Finally, deploy your Flask app on PythonAnywhere as usual, ensuring your WSGI configuration is correct.

Important Considerations

Always check the compatibility of the browser and driver versions before deployment.

It’s essential to test the entire automation process locally and again in the deployed environment to catch potential errors before they become critical issues.

Conclusion

Deploying a Selenium-based Flask application on PythonAnywhere is a feasible task if you follow the proper steps regarding browser and driver compatibility. By sticking to the default installations provided by PythonAnywhere, you can avoid most common pitfalls associated with using webdriver-manager. With this approach, you can automate tasks smoothly and efficiently.

If you have any further questions or need assistance with your deployment, feel free to ask!