effective java builder pattern for python

builder_example.py

#-*- coding: utf-8 -*-

class NutritionFacts(object):

    def __init__(self, builder):
        self.serving_size = builder.serving_size
        self.servings = builder.servings
        self.calories = builder.calories
        self.fat = builder.fat
        self.sodium = builder.sodium
        self.carbohydrate = builder.carbohydrate

    class Builder(object):

        def __init__(self, serving_size, servings):
            self.serving_size = serving_size
            self.servings = servings
            self.calories = None
            self.fat = None
            self.sodium = None
            self.carbohydrate = None

        def set_calories(self, val):
            self.calories = val
            return self
        
        def set_fat(self, val):
            self.fat = val
            return self

        def set_sodium(self, val):
            self.sodium = val
            return self

        def set_carbohydrate(self, val):
            self.carbohydrate = val
            return self

        def build(self):
            return NutritionFacts(self)


nf = NutritionFacts.Builder(100, 5) \
    .set_calories(300) \
    .set_fat(10) \
    .set_sodium(20) \
    .set_carbohydrate(30) \
    .build()

print(nf.calories)