What is the possibility of using a Python app, deployed online, that has access to a users local disk?
You'd have to create a "client" and "server" type of interface to do this.  So it wouldn't be a solely JavaScript with Python on the server program.  They'd have to have something running on their end as well, communicating in the background.
HTML5 allows some local storage, but not what you're looking for.
I currently have a local python application that scans a users drive, maps it into a tree and displays this information with javascript. I would really like to try to develop something with a Drop-Box like system to manage drive trees. 
I have searched and read that App Engine specifically doesn't allow access to a user's local disk. Is there a way to use webpy or something else to access a user's local drive to create a tree directory out of it?