Apply automatic pep8 fixes from QuickFix window
$ autopep8 --in-place spam.py
$ git difftool spam.py  # check edits in gVim, write to file
$ git commit spam.py -m "Fix bad PEP8 formatting"

" copy this to your vimrc or source it

" tells vim not to automatically reload changed files
set noautoread

function! DiffWithSaved()
  let filetype=&ft
  diffthis
  vnew | r # | normal! 1Gdd
  diffthis
  exe "setlocal bt=nofile bh=wipe nobl noswf ro ft=" . filetype
endfunction

" sets up mappings to function

com! DiffSaved call DiffWithSaved()
map <Leader>ds :DiffSaved<CR>

" run these commands after sourcing the above function

" % expands to filename (also %:h to head, %:t to tail)
" if it throws an error, just do :cd %:h first

:!autopep8 --in-place %
:DiffSaved