This can be achieved this is EditBox.
With some customization through it s preferences you can get to some nice code blocks highlighting of python code (or any other where blocks are signified with whitespace).
It is highly customizable and can achieve the vertical rules codekana style, and various other layouts.
The problem is it doesn t work on PyDev editor from what I see (at least for now). I ve opened a feature request for it.
If it s any good, you can still view it s layout when opening a python file with right click "Open With/Text editor". From version 0.20, EditBox fully supports PyDev.
I also tried AnyEdit which has some whitespace highlighting amongst other features, but was not too happy with the results. For example, I had to press they re "show whitespace" button after each change to show the background, and it s not very visually pleasing (it uses eclipse s annotations to highlight whitespace).