python3
Python 3.5.3 (default, Jan 19 2017, 14:11:04) 
[GCC 6.3.0 20170118] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import g
KeyboardInterrupt
>>> from gi.repository import Gtk
__main__:1: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
>>> dlg = Gtk.MessageDialog()
>>> dlg.run()