autocmd BufRead,BufEnter *.py nmap <silent><F5> <ESC> :call CheckPythonSyntax()<CR>
autocmd BufRead,BufEnter *.py imap <silent><F5> <ESC> :call CheckPythonSyntax()<CR>

function CheckPythonSyntax()
  " Write the current buffer to a temporary file, check the syntax and
  " if no syntax errors are found, write the file
  let curfile = bufname("%")
  let tmpfile = tempname()
  silent execute "write! ".tmpfile
  let output = system&#40;"python -c \"__import__('py_compile'&#41;.compile(r'".tmpfile."')\" 2>&1")
  if output != ''
    " Make sure the output specifies the correct filename
    let output = substitute(output, fnameescape(tmpfile), fnameescape(curfile), "g")
    echo output
  else
    write
  endif
  " Delete the temporary file when done
  call delete(tmpfile)
endfunction