Logged In: YES 
user_id=495142

When you install Python in Windows, you will get 
"Edit with IDLE" entry in the context menu for *.py file.
The entry launches the pythonw.exe with the name of
*.py file as one of the sys.argv[] parameters.

See the registry: 
HKEY_CLASSES_ROOT\Python.File\shell\Edit with IDLE\command

There you will see:
"C:\Python24\pythonw.exe" "C:\Python24\Lib\idlelib\idle.pyw"
-n -e "%1"

I thought the file name given here as "%1" would be what
open(2) accepts.