You have to try it!

class Pizza(Fields.name.size):
    pass

>>> Pizza("Pepperoni", "large")
Pizza(name='Pepperoni', size='large')

class Pizza(Fields.name.ingredients.crust.size):
    pass

>>> Pizza("Funghi", ["mushrooms", "mozarella"], "thin", "large")
Pizza(name='Funghi', ingredients=['mushrooms', 'mozarella'],
      crust='thin', size='large')

Before we consider this for inclusion in the standard library ...

„Don't speak around saying that I like it.”

”Are Python programmers that lazy?” --Some Java developer

„Is it some Ruby thing?”

„WHAT?!?!”

„I don't think it should work ...”

Of course it has support for defaults!

class Pizza(Fields.name.crust["thing"].size["large"]):
    pass

>>> Pizza("Funghi", crust="thick")
Pizza(name='Funghi', crust='thick', size='large')

https://github.com/ionelmc/python-fields

Sorry!