highlight ExtraWhitespace ctermfg=white ctermbg=red guibg=red guifg=white
match ExtraWhitespace /\(\s\+$\|^\s*\t\|,[^ ]\|[;]$\|#[^ ].\|def [A-Z]\|class [a-z]\)/
autocmd BufWinEnter * match ExtraWhitespace /\(\s\+$\|^\s*\t\|,[^ ]\|[;]$\|#[^ ].\|def [A-Z]\|class [a-z]\)/
autocmd BufWinLeave * call clearmatches()

set et
set sw=4
set ai
set smarttab