Python Design Patterns - Abstract Factory


The abstract factory pattern is also called factory of factories. This design pattern comes under the creational design pattern category. It provides one of the best ways to create an object.

It includes an interface, which is responsible for creating objects related to Factory.

How to implement the abstract factory pattern?

The following program helps in implementing the abstract factory pattern.

class Window:
   __toolkit = ""
   __purpose = ""

   def __init__(self, toolkit, purpose):
      self.__toolkit = toolkit
      self.__purpose = purpose
   def getToolkit(self):
      return self.__toolkit
   def getType(self):
      return self.__purpose

class GtkToolboxWindow(Window):
   def __init__(self):
      Window.__init__(self, "Gtk", "ToolboxWindow")

class GtkLayersWindow(Window):
   def __init__(self):
      Window.__init__(self, "Gtk", "LayersWindow")

class GtkMainWindow(Window):
   def __init__(self):
      Window.__init__(self, "Gtk", "MainWindow")

class QtToolboxWindow(Window):
   def __init__(self):
      Window.__init__(self, "Qt", "ToolboxWindow")

class QtLayersWindow(Window):
   def __init__(self):
      Window.__init__(self, "Qt", "LayersWindow")

class QtMainWindow(Window):
   def __init__(self):
      Window.__init__(self, "Qt", "MainWindow")

# Abstract factory class
class UIFactory:
   def getToolboxWindow(self): pass
   def getLayersWindow(self): pass
   def getMainWindow(self): pass

class GtkUIFactory(UIFactory):
   def getToolboxWindow(self):
      return GtkToolboxWindow()
   def getLayersWindow(self):
      return GtkLayersWindow()
   def getMainWindow(self):
      return GtkMainWindow()

class QtUIFactory(UIFactory):
   def getToolboxWindow(self):
      return QtToolboxWindow()
   def getLayersWindow(self):
      return QtLayersWindow()
   def getMainWindow(self):
      return QtMainWindow()

if __name__ == "__main__":
   gnome = True
   kde = not gnome
   if gnome:
      ui = GtkUIFactory()
   elif kde:
      ui = QtUIFactory()
   toolbox = ui.getToolboxWindow()
   layers = ui.getLayersWindow()
   main = ui.getMainWindow()
   print "%s:%s" % (toolbox.getToolkit(), toolbox.getType())
   print "%s:%s" % (layers.getToolkit(), layers.getType())
   print "%s:%s" % (main.getToolkit(), main.getType())


The above program generates the following output −

Abstract Factory Pattern


In the above program, the abstract factory creates objects for each window. It calls for each method, which executes the output as expected.