python - 嵌套for循环迭代多个字典，有没有更简单的方法？

Question

所以我懒惰的屁股正试图在 python 3.x 中创建一个膳食计划生成器，这样我就不必每个星期五都花 30 分钟来弄清楚我应该吃什么，但我是编码新手并且正在努力解决一些问题。我仍在学习 Udemy 类(class)，但我想亲自动手编写代码以正确学习。任何人，这是我到目前为止所得到的:

class Meals():

    def __init__(self,breakfast,lunch,dinner):
        self.breakfast=breakfast
        self.lunch=lunch
        self.dinner=dinner
    def __str__(self):
        return f"Breakfast will be {self.breakfast}.\nLunch will be        {self.lunch}.\nDinner will be {self.dinner}."
    def cost(self):
        day_meals=[self.breakfast,self.lunch,self.dinner]
        day_cost=0
        for i in day_meals:
            for ingredient in i:
                for key,value in Shop2.items():
                    if key in ingredient:
                        day_cost+=value
        return f"Today will cost £{round(day_cost,2)}."

如果我这样做:

    monday_meals=Meals(random.choice(list(breakfasts.keys())),random.choice(list(lunches.keys())),random.choice(list(dinners.keys())))

然后调用 monday_meals.breakfast，然后我得到我想要的结果，从“早餐”字典中随机选择的键，但每当我调用:monday_meals.cost()然后我得到 0 英镑且没有显示任何错误。

作为引用，我的测试词典如下:

breakfasts={"a bowl of Rice Crispies":["cereal_1","milk"],"Weetabix":["cereal_2","milk"],"some Golden Grahams":["cereal_3","milk"],"toast":["bread","butter"],"scrambled eggs":["egg","egg","milk"]}

lunches={"cereal bars":["cereal_bar","cereal_bar"],"a boring ham sandwich":["bread","ham"],"some fruit":["banana","apple"],"salad":"salad_bag"}

dinners={"Student Meal #1":["mince","red_sauce","pepper","onion"],"Student Meal #2":["c_breast","white_sauce","onion","pepper"],"Student Meal #3":["egg","pepper","tomato","onion"]}

Shop2={"egg":0.3,"tomato":0.35,"pepper":0.33,"onion":0.4,"mince":1.2,"c_breast":0.7,"rice":0.8,"red_sauce":1.4,"white_sauce":1.5,"cereal_1":0.4,"milk":0.13,"cereal_2":0.35,"cereal_3":0.45,"bread":0.04,"butter":0.04,"cereal_bar":0.75,"ham":0.25,"banana":0.3,"apple":0.3,"salad":0.75}

如果能找到一种更简单的方法来计算一天的膳食费用，我将不胜感激。

Answer 1

您可以通过以下方式实现您的设计:

# inside your class:

@staticmethod
def calculate_meal_cost(ingredients, shopdict):
    return sum(shopdict[ingredient] for ingredient in ingredients)

@property
def cost(self):
    breakfast_cost = self.calculate_meal_cost(breakfasts[self.breakfast], Shop2)
    lunch_cost = self.calculate_meal_cost(lunches[self.lunch], Shop2)
    dinner_cost = self.calculate_meal_cost(dinners[self.dinner], Shop2)
    return breakfast_cost + lunch_cost + dinner_cost

然后:

meal = Meal(...)  # however you pick your meals is fine
meal.cost  # note: no parens