Flask file upload and download

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Serialization in Django. Signals in Django. Regular Expressions in Python. Integration tests in Django. Home Python How to upload and download files using Flask. Table of Contents. Share 0 Facebook Twitter Pinterest Email. You may also like. Regular Expressions in Python November 26, How to use Lambda in Python November 2, Socket Programming in Python November 1, It basically works like this:. The application accesses the file from the files dictionary on the request object.

So first we need a couple of imports. Most should be straightforward, the werkzeug. Why do we limit the extensions that are allowed? Also make sure to disallow. Next the functions that check if an extension is valid and that uploads the file and redirects the user to the URL for the uploaded file:.

We should also check for file extension that the user is uploading as there would be some specific type of file that the site can process. Also there is security issue if the user can upload any type of file. User might upload html file that can cause XSS cross site-scripting problems. For this post, we only need pdf file extensions as this Flask app would remove watermark from pdf files created by CamScanner App Famous App for scanning documents through Mobile Camera.

Pdf files would have watermark at the bottom similar to what is shown in the image below :. Function checks the filename for allowed file extension and if file type is supported the function returns True otherwise it returns False. We can add more extension types in allowed extensions set for supporting different type of file uploads.