You can do this with PyObjC as well, and by using the ObjC methods via Python, off the top of my head, without actually writing a quickie app, you would import objc, appkit, foudation. Then just use the exposed classes. dlg = NSAlert_alloc_init_()
and apply the options you want, then call dlg.runmodal_()

I have used this in several PyObjC apps, as well as in some of my personal scripts that are command line python scripts or applets.