python的Simple Factory模式

根据上图的simple factory代码为：

 

代码清单1：shape.py
class Shape:
    # 绘制图形
    def draw(self):
        pass
    # 擦除图形
    def erase(self):
        pass
代码清单2：circle.py
class Circle (Shape):
    def __init__(self, radius = 0):
        self.__radius = radius
    # 绘制圆形
    def draw(self):
        print "Draw Circle"
    # 擦除圆形
    def erase(self):
        print "Erase Circle"
    # 半径的取值方法
    def getRadius(self):
        return self.__radius
    # 半径的赋值方法
    def setRadius(self, radius):
        self.__radius = radius
代码清单3：rectangle.py
class Rectangle (Shape):
    def __init__(self, width = 0, height = 0):
        self.__width = width
        self.__height = height
    # 绘制矩形
    def draw(self):
        print "Draw Rectangle"
    # 擦除矩形
    def erase(self):
        print "Erase Rectangle"
    # 宽度的取值方法
    def getWidth(self):
        return self.__width
    # 宽度的赋值方法
    def setWidth(self, width):
        self.__width = width
    # 高度的取值方法
    def getHeight(self):
        return self.__height
    # 高度的赋值方法
    def setHeight(self, height):
        self.__height = height

代码清单4：diamond.py
class Diamond (Shape):
    def __init__(self, width = 0, height = 0):
        self.__width = width
        self.__height = height
    # 绘制菱形
    def draw(self):
        print "Draw Diamond"
    # 擦除菱形
    def erase(self):
        print "Erase Diamond"
    # 宽度的取值方法
    def getWidth(self):
        return self.__width
    # 宽度的赋值方法
    def setWidth(self, width):
        self.__width = width
    # 高度的取值方法
    def getHeight(self):
        return self.__height
    # 高度的赋值方法
    def setHeight(self, height):
        self.__height = height
代码清单5：shapefactory.py
class ShapeFactory:
    def factory(self, which):
        if which == "Circle":
            return Circle()
        elif which == "Rectangle":
            return Rectangle()
        elif which == "Diamond":
            return Diamond()
        else:
            return None

使用simple factory的简单例子：
fac = ShapeFactory()
shape = fac.factory("Diamond")
if shape != None:
    shape.draw()