Making a Memorable Dropbox Public File Redirect with Flask

Files stored in your Dropbox Public folder are viewable by anyone with access to the URL, which is long and hard to remember but unique. Flask is a microframework for making lightweight dynamic websites in Python. In this post, I’ll be demonstrating how to make a simple webapp with Flask that redirects requests to your Dropbox public folder, and hosting it.

Finding your user constant

Every file in your Public folder is available at the URL https://dl.dropbox.usercontent.com/u/[user constant]/[filename]. To find your user constant, open your Dropbox Public folder, right click on a file, select Dropbox > Copy Public Link, and paste into a text editor.

Writing the app

Uncomment line 2, and define USER_CONSTANT to be the constant number you found previously.

Lines 6-8 return usage message if the app is accessed without a filename, lines 10-12 redirect to the file with the specified name in your Public folder if /[filename] is accessed, and the other lines import and run Flask. That’s it!

Hosting the app

While you could run this app locally, it’s not exceptionally useful limited to your computer. To host it for free, we’ll use Heroku. Heroku uses git to deploy your code. Make an account and create a new app, with a short, memorable name. It’ll generate a customized git clone command. Run it in your terminal:

git clone git@heroku.com:[your app name].git -o heroku

cd [your app name]

Copy app.py to this directory, then we have to make two more files for Heroku to know what to do with our app.

The Procfile tells Heroku how to run our app. In this case, by running app.py

requirements.txt lists all the packages our app depends on, which Heroku will install at compiletime.

Now, add these three files to the repository, commit, and push:

git add app.py Procfile requirements.txt

git commit -m "Initial Commit"

git push heroku master

Wait for compilation to finish, then check on your app at http://[your app name].herokuapp.com/. If you see the usage message, it works! Now you can use the simpler http://[your app name].herokuapp.com/[filename] to access your Public files.

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