For Python 'SPE' or 'ERIC3' are great.
I know for sure that SPE supports highlighting whitespace. Probable ERIC3 as well.
Also you can let the editors save without trailing spaces.
'kate' supports highlighting whitespace as well as tabs and can also remove trailing spaces and/or highlight them.
At the moment I'm using 'KDevelop' because it supports vertical selection which is very usefull at times.