const win32ui.PD_RETURNDEFAULT;

If this flag is set, the PrintDlg function does not display the dialog box. Instead, it sets the hDevNames and hDevMode members to handles toDEVMODE and DEVNAMES structures that are initialized for the system default printer. Both hDevNames and hDevMode must be NULL, or PrintDlg returns an error. If the system default printer is supported by an old printer driver (earlier than Windows version 3.0), only hDevNames is returned; hDevMode is NULL.