Flask download file empty

I previously suggested using the user id as a filename, when saving an uploaded avatar image. This was the way the images were saved:.

Alternatively, the uploads can be saved to a directory outside of the static folder, and then a new route can be added to serve them. In the example app. To serve these files from that location, we can implement the following route:. One advantage that this solution has over storing uploads inside the static folder is that here you can implement additional restrictions before these files are returned, either directly with Python logic inside the body of the function, or with decorators.

Let's use this implementation idea to show uploaded files in our example application. Here is a new complete version of app. In addition to the new upload function, the index view function gets the list of files in the upload location using os.

The index. With these changes, every time you upload an image, a thumbnail is added at the bottom of the page:. When users upload private files to the application, additional checks need to be in place to prevent sharing files from one user with unauthorized parties.

The solution for these cases require variations of the upload view function shown above, with additional access checks. A common requirement is to only share uploaded files with their owner.

A convenient way to store uploads when this requirement is present is to use a separate directory for each user. Below you can see a possible implementation of this technique, once again assuming Flask-Login is used:.

Up until now we have relied on the native file upload widget provided by the web browser to initiate our file uploads. I'm sure we can all agree that this widget is not very appealing. Not only that, but the lack of an upload progress display makes it unusable for uploads of large files, as the user receives no feedback during the entire upload process. While the scope of this article is to cover the server side, I thought it would be useful to give you a few ideas on how to implement a modern JavaScript-based file upload widget that displays upload progress.

The good news is that on the server there aren't any big changes needed, the upload mechanism works in the same way regardless of what method you use in the browser to initiate the upload. That's basically it! You can now drop files and they'll be uploaded to the server with a progress bar and a final indication of success or failure.

If the file upload fails, either due to the file being too large or invalid, dropzone wants to display an error message. Because our server is currently returning the standard Flask error pages for the and errors, you will see some HTML gibberish in the error popup.

To correct this we can update the server to return its error responses as text. The error for the file too large condition is generated by Flask when the request payload is bigger than the size set in the configuration.

To override the default error page we have to use the app. The second error condition is generated by the application when any of the validation checks fails. In this case the error was generated with a abort call. Instead of that the response can be generated directly:. The final change that I'm going to make isn't really necessary, but it saves a bit of bandwidth.

For a successful upload the server returned a redirect back to the main route. This caused the upload form to be displayed again, and also to refresh the list of upload thumbnails at the bottom of the page. None of that is necessary now because the uploads are done as background requests by dropzone, so we can eliminate that redirect and switch to an empty response with a code The dropzone.

You can also look for other JavaScript file upload libraries, as they all follow the HTTP standard, which means that your Flask server is going to work well with all of them.

This was a long overdue topic for me, I can't believe I have never written anything on file uploads! I'd love you hear what you think about this topic, and if you think there are aspects of this feature that I haven't covered in this article.

In your project folder, create and enable it like this:. For flask to run correctly, some environment variables need to be set. The ones needed by your project can be seen in the Dockerfile or Makefile files. For a list of all other optional environment variables, check this link.

When using docker , you can easely set them inline before each run. When using docker-compose , set them in the yaml configuration file for each environment.

If instantiated somewhere else, just import them here and you should be fine. They're are all self explanatory and commented. Override it to quickly add custom extension setups, simple views, context processors, etc.

It already has some sensitive defaults for most use cases. Use it like this:. You can also add your own. No setup required. It has nice Formatting and this post also covers "How to ignore or avoid the weblogic informational messages while running the WLST script" Copy the Script given below…. Skip to content. Table of Contents. More from Middleware Inventory. Remote Server - File System Lister [Linux] Have you ever had the requirement of logging in to the Nnumber of remote servers without keybased authentication and get the mount point information and save it as CSV Report or Print it with a good console formatting.

Apr 30, Apr 26, Feb 10, May 16, Mar 31, Dec 21, Jun 7, May 29, Jun 14, Jun 13, Jul 1, Sep 29, Jul 6, Configure Nginx Credits Licenses. Requirements Python 2. A password is never required to download files, only to upload them. Use hashed passwords By default, Flaskup! Configure Flaskup! Licenses Flaskup! About A simple Flask application to share files Resources Readme.