from __future__ import generators

import random

class polyShapeFactory:

factories = {}

def addFactory(id, shapeFactory):

ShapeFactory.factories.put[id] = shapeFactory

addFactory = staticmethod(addFactory)

def createShape(id):

if not ShapeFactory.factories.has_key(id):

ShapeFactory.factories[id] = \

eval(id + '.Factory()')

return ShapeFactory.factories[id].create()

createShape = staticmethod(createShape)

class Shape(object): pass

class Circle(Shape):

def draw(self): print("Circle.draws")

def erase(self): print("Circle.erase")

class Factory:

def create(self): return Circle()

class Square(Shape):

def draw(self):

print("Square.draw")

def erase(self):

print("Square.erase")

class Factory:

def create(self): return Square()

def shapeNameGen(n):

types = Shapes.__subclasses__()

for i in range(n):

yield random.choice(types).__name__

shapes = [ShapeFactory.createShape(i)

for i in shapeNameGen(7) ]

for shape in shapes:

shape.draw()

shape.erase()