Solving The submitted data was not a file Error in Django REST Framework with Multipart Form Data

Learn how to troubleshoot and fix the `The submitted data was not a file. Check the encoding type on the form.` error in Django REST Framework when using multipart/form-data with nested serializers and file uploads.
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Solving The submitted data was not a file Error in Django REST Framework with Multipart Form Data

When working with file uploads in Django REST Framework (DRF), you might encounter a frustrating error: The submitted data was not a file. Check the encoding type on the form. This often arises when dealing with multipart/form-data, particularly when combined with nested serializers. In this post, we'll break down the issue and provide a solution that will help you overcome this error.

Understanding the Problem

The error typically occurs during the parsing of multipart form data when you're sending files alongside complex data structures. In your case, you mentioned an instance where you were using nested serializers along with file uploads and faced the AttributeError associated with the to_internal_value() method of the FileField. Here’s a brief overview of how this error crops up:

Multipart Form Data: You're using multipart/form-data to send data, including images/files.

FileField Processing: When DRF tries to process the uploaded file, it encounters an issue where the expected name and size attributes are missing.

List vs. FileIssue: The file upload is being interpreted as a list rather than an InMemoryUploadedFile, causing the parsing to fail.

Solution: Adjusting the View

Code Example

Below is an example of how you can adjust your view to handle the uploaded files correctly:

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Key Changes Implemented

Super Call: After adjusting the request data, we call the appropriate super() method to ensure DRF processes the data correctly.

Conclusion

While encountering the The submitted data was not a file error in Django REST Framework can be daunting, understanding the underlying mechanics of multipart form parsing can lead to effective solutions. By customizing your views as illustrated above, you can overcome this issue and successfully handle file uploads along with your nested serializers.

Final Thoughts

Be sure to thoroughly test your implementation to confirm that both file uploads and other nested data are being processed correctly. Happy coding!