Скачать или смотреть Understanding the Request form is empty Issue in Flask

Unlock the mystery of the Flask request form showing empty. Learn how to extract data properly from HTML forms in your Flask applications with this easy-to-follow guide.
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This video is based on the question https://stackoverflow.com/q/64094374/ asked by the user 'walid' ( https://stackoverflow.com/u/13067358/ ) and on the answer https://stackoverflow.com/a/64094894/ provided by the user 'Linh Nguyễn Ngọc' ( https://stackoverflow.com/u/13920135/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Request form is empty Issue in Flask: A Simple Guide

When working with Flask, a common issue developers face is receiving an empty dictionary when attempting to retrieve data from a submitted form. This can be frustrating, especially if you've confirmed that the form elements have values. In this guide, we will explore a typical scenario that leads to this issue and provide practical solutions to ensure your Flask application handles form data correctly.

The Problem

Imagine you have an HTML form designed to send input to a Flask server. Here’s a simplified version of what that form might look like:

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

After populating the form fields dynamically, you may use JavaScript to log their values:

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

Despite seeing values in the console, when you check the server-side, you find that the request.form yields an empty dictionary. Why does this happen?

The Solution

In many cases, the issue arises from how you attempt to access form data in Flask. Here’s how you can resolve it step by step.

Step 1: Correctly Retrieve Form Data

Instead of trying to return the entire request.form, it’s better to individually retrieve the values you need. Modify your route handler like this:

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

Here’s what we did:

Retrieved individual form values using request.form.get('key_name')

Added print statements to verify the values received

Step 2: Redirecting After Form Submission

To ensure that users are still directed back to the previous page after submission, use redirect(request.referrer). This way, they won’t see an empty form upon returning.

Step 3: Render the Template Conditionally

If needed, you can also choose to render another template based on the logic implemented in your route. Just ensure that you return the expected responses as shown in the revised function.

Conclusion

Encountering an empty request form in Flask can be a nuisance; however, understanding how to access form data correctly can resolve this problem effectively. By explicitly retrieving the values and using print statements for verification, you can ensure that your Flask application receives the data as expected.

In summary:

Check your form element names: Ensure they match what you're accessing in Flask.

Print values for verification: Helps track what's being submitted.

Redirect or render appropriately: Improve user experience after submission.

By following these guidelines, you can avoid the frustration of empty requests and streamline your Flask application’s functionality. Happy coding!