self.addButton = Gtk.ToolButton()
self.addButton.set_property('visible', True)
self.addButton.set_property('can_focus', False)
self.addButton.set_property('use_action_appearance', False)
self.addButton.set_property('use_underline', False)
self.addButton.set_property('icon_name', 'list-add-symbolic')
self.listTools.add(self.addButton)
Python GTK3 Treeview buttons