Скачать или смотреть Fixing the request.files Empty Issue in Flask File Uploads

Learn how to effectively handle multiple file uploads in Flask by using `MultiDict`. This guide provides a clear solution to the common issue of `request.files` being empty during file uploads.
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This video is based on the question https://stackoverflow.com/q/66459131/ asked by the user 'DarkMath' ( https://stackoverflow.com/u/10975692/ ) and on the answer https://stackoverflow.com/a/66475346/ provided by the user 'DarkMath' ( https://stackoverflow.com/u/10975692/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the request.files Empty Issue in Flask File Uploads

When working with file uploads in Flask, developers often encounter the frustrating issue of request.files being empty—especially when trying to upload multiple files. This problem can halt progress and leave you searching for answers. In this guide, we will discuss a solution to this common predicament and ensure that your uploads run smoothly in Flask.

The Problem: Uploading Multiple Files

Here is a simplified code snippet that illustrates the problem:

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

In this example, the first file upload request succeeds, but the second request fails because it does not populate request.files. This leads to an assertion error, indicating that no files were successfully uploaded.

The Solution: Using MultiDict

To tackle this issue, you can utilize Flask's MultiDict, which is designed to handle multiple entries with the same key. Here's how to implement this solution:

Updated Code Example

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

Explanation of Key Changes

Use of MultiDict: The modified code replaces the normal dictionary with MultiDict for data_2, which allows for multiple files to be uploaded under the same name (in this case, file).

Consistent Testing: The test client is used to post data to the endpoint, ensuring that both scenarios (single and multiple files) return a successful status code.

Sample Output

After making these changes, you should see output indicating that the files have been uploaded successfully:

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

Conclusion

Uploading multiple files in Flask can lead to unexpected issues with request.files being empty. By employing MultiDict, you can seamlessly handle multiple file uploads without encountering assertion errors. This solution enhances data handling in your Flask application and allows you to focus on building functionality rather than troubleshooting errors.

If you found this guide helpful, share it with others experiencing similar issues and elevate your Flask development journey!