Do you have https://gist.github.com/4034526 working already?

http://omz-forums.appspot.com/pythonista/post/6675908186341376

Once dropboxlogin is working, you can:

Use https://www.dropbox.com/developers/core/docs/python#DropboxClient.get_file

with client.get_file('/magnum-opus.txt') as in_file: the_data = in_file.read()