When I run "python -m idlelib.idle -sc [command] from the command line, IDLE runs the startup file, but then pops up an error message saying "the Python Shell window is already executing a command;please wait until it is finished." When the error window is closed, the command executes, unless the main Python Shell has already been closed, in which case a traceback occurs:
Traceback (most recent call last):
  File "C:\Python27\lib\runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Python27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Python27\lib\idlelib\idle.py", line 11, in <module>
    idlelib.PyShell.main()
  File "C:\Python27\lib\idlelib\PyShell.py", line 1602, in main
    shell.interp.execsource(cmd)
AttributeError: 'NoneType' object has no attribute 'execsource'