I use nano to do quick edits or test out ideas in a dirty and quick script. If you use python, it's a good idea to have proper indentation. Nano has a default tab size of 8.

Edit ~/.nanorc:

set tabsize 4
set tabstospaces

If you have a file and want to convert tabs to spaces, quick one liner:

expand -4 tabbed.py > spaced.py

Now, if you want to work with a different tab size- lets say you want to edit a two space JS file, but don't want to change the default:

nano -T 2 Gruntfile.js