new_pizza_maker.py

# We create dedicated pizza maker classes, each class
# creates just 1 type of pizza.
# We will also register the makers.

@register_pizza_maker
class _PizzaMargheritaMaker:
  pizza_class_name = "PizzaMargherita"
  
  def create(with_bazil=True):
    pizza = PizzaMargherita(with_bazil=True)
    .... <populate all the other fields>
    return pizza

@register_pizza_maker
class _PizzaPestoMaker:
  pizza_class_name = "PizzaPesto"
  
  def create(cheeze_type, with_arugula=True):
    ...

class PizzaMaker:
  
  # We will again promote "ptype" and name it explicitly.
  def create_pizza(self, ptype, **pizza_properties):
    
    # get_pizza_makers will also raise UnknownPizaType if needed
    pizza_maker = get_pizza_makers(ptype)
    # The actual pizza maker will validate pizza_properties
    pizza = pizza_maker.create(**pizza_properties)
    
    return pizza

registry.py

# This will be our registry of all existing pizza makers
ALL_PIZZA_MAKERS = {}

# With this decorator, we will register Maker classes
def register_pizza_maker(maker_class):
    if maker_class.pizza_class_name is None:
        raise ValueError("Missing pizza_class_name for pizza maker %s" % maker_class.__name__)

    ALL_PIZZA_MAKERS[maker_class.pizza_class_name] = maker_class

    return maker_class
  
# With this getter function, we will resolve pizza class names to pizza makers.
def get_pizza_maker(pizza_type: str):
  maker = ALL_PIZZA_MAKERS.get(pizza_type)
  if maker is None:
    raise UnknownPizaType(pizza_type)
    
  return maker