On windows
  type settings in the search input box
  type path in the find a setting input box
  select edit environment variables for your account
  under the user variables section click new
  type PYTHONSTARTUP in the variable name input box
  type the path to this file (e.g. d:\python\setup.py) in the variable value input box
  click OK
  click OK
  
  to start python run terminal or cmd.exe
  type py
  or make a shortcut of course

  For editing
    textpad is free and I have been using it for years
    it does automatic indentation 
       (configure - preferences - document classes - default - tabulation)
    and shows line numbers
       (configure - preferences - view)