Python Factory with __new__()

NewFactory.py

# https://stackoverflow.com/a/5961102

class Shape(object):
    def __new__(cls, *args):
        selector = args[0]
        print('factory build:', selector)
        if cls is Shape:
            # Create a subclassed shape from a name
            if selector == 'rectangle': return super(Shape, cls).__new__(Rectangle)
            if selector == 'triangle': return super(Shape, cls).__new__(Triangle)
            raise 'unrecognized shape'
        else:
            # a subclassed shape was created.  return that one directly.
            print('factory initialize:', selector)
            return super(Shape, cls).__new__(cls)

    def __init__(self, selector, junk):
        """Base Shape object.  Contains factory and common methods

        Args:
            selector: The type of shape to build.
            junk: The second parameter.

        Returns:
            Nothing.
        """

        print("shape init")
        self.desc = junk
        self.edge_count = None

        return

    @property
    def number_of_edges(self):
        return self.edge_count

class Triangle(Shape):
    def __init__(self, selector, junk):
        print("triangle init")
        super().__init__(selector, junk)

        self.edge_count = 3
        return

@property
def name(self):
    return 'Triangle'


class Rectangle(Shape):
    def __init__(self, selector, junk):
        print("rectangle init")
        super().__init__(selector, junk)

        self.edge_count = 4
        return

    @property
    def name(self):
        return 'Rectangle'


if __name__ == '__main__':
    shape = Shape('rectangle','big')
    print('{} has {} edges'.format(shape.name, shape.number_of_edges))