from gi.repository import Gtk, GLib

child = Gtk.Window(type=Gtk.WindowType.POPUP, title="child", default_width=200, default_height=200)
child.show_all()

parent = Gtk.Window(title="parent", default_width=300, default_height=300)
child.set_transient_for(parent)

parent.show_all()

# only parent shows up after this

GLib.unix_signal_add(0, 2, Gtk.main_quit)
Gtk.main()
