gtk.Bin — an abstract base class defining a container with just one child.
gtk.Bin is an abstract base class defining a widget that is a container with just one child. It is useful for deriving subclasses, since it provides the common code needed for handling a single child widget. Many PyGTK widgets are subclasses of gtk.Bin, including gtk.Window, gtk.Button, gtk.Frame, gtk.HandleBox, and gtk.ScrolledWindow.