new_contents: import vim
  import venom
  
  
  def run_python_file():
      vim.command("w !python<CR>")
  
  
  def append_hello_world():
      print "APPENDING HELLO WORLD"
      # vim.current.buffer.append("Hello World")
  
  
  venom.nnoremap("<leader><f7>", append_hello_world)
  print "MERCURY HAS RUN"
  
subject: move python code into .py file.