如何在不调用所有比较的情况下迭代if语句？

Question

我有一些固定的变量，我想与一些用户输入进行比较。根据结果，我想打印一个结果，但是如何比较变量，而不调用许多if语句，并且必须将每个语句相互比较？

#Nutrition Class and methods

class Nutrition():
    def __init__(self):
        self.pro = pro
        self.vit = vit
        self.carb = carb
        self.fat = fat
        self.mineral = mineral

    def comp_nut(self, pro, vit, fat, carb, mineral):
        if(self.pro >= req_pro) and (self.vit>= req_vit) and (self.fat >= req_fat) and (self.carb >= req_carb) and (self.mineral >= req_min):
            print("You are healthy")
        elif (self.pro >= req_pro) and (self.vit>= req_vit) and (self.fat >= req_fat) and (self.carb >= req_carb) and (self.mineral < req_min):
            print("Mineral is low!")
            print("Require Amount is "+ str(req_min))
        elif (self.pro >= req_pro) and (self.vit>= req_vit) and (self.fat >= req_fat) and (self.carb < req_carb) and (self.mineral >= req_min):
            print("Carb is low!")
            print("Require Amount is "+ str(req_carb))
        elif (self.pro >= req_pro) and (self.vit>= req_vit) and (self.fat < req_fat) and (self.carb >= req_carb) and (self.mineral >= req_min):
            print("Fat is low!")
            print("Require Amount is "+ str(req_fat))
        elif (self.pro >= req_pro) and (self.vit < req_vit) and (self.fat >= req_fat) and (self.carb >= req_carb) and (self.mineral >= req_min):
            print("Vitamin is low!")
            print("Require Amount is "+ str(req_vit))
        elif (self.pro < req_pro) and (self.vit>= req_vit) and (self.fat >= req_fat) and (self.carb >= req_carb) and (self.mineral >= req_min):
            print("Protein is low!")
            print("Require Amount is "+ str(req_pro))
        else:
           print('More than 1')

# User Input

pro = int(input("Enter Protein: "))
vit = int(input("Enter Vitamin: "))
fat = int(input("Enter Fat: "))
carb = int(input("Enter Carbs: "))
mineral = int(input("Enter Mineral: "))

Answer 1

一次测试一件事，如下所示：

def comp_nut(self, pro, vit, fat, carb, mineral):
    if (self.mineral < req_min):
        print("Mineral is low!")
        print("Require Amount is "+ str(req_min))
    elif (self.carb < req_carb):
        print("Carb is low!")
        print("Require Amount is "+ str(req_carb))
    elif (self.fat < req_fat):
        print("Fat is low!")
        print("Require Amount is "+ str(req_fat))
    elif (self.vit < req_vit):
        print("Vitamin is low!")
        print("Require Amount is "+ str(req_vit))
    elif (self.pro < req_pro):
        print("Protein is low!")
        print("Require Amount is "+ str(req_pro))
    else:
        print("You are healthy.")

这将打印缺陷检查成功的第一条消息，或"You are healthy“。如果所有检查都失败。

Answer 2

为了避免每次重复所有字段，我会这样做：

from collections import namedtuple

# Use a namedtuple so that we don't have to write __init__()
# and so that all the field names are stored in _fields.
class Nutrition(namedtuple('Nutrition', 'protein vitamin fat carb mineral')):

    # List of minimum requirement per each
    # field (these are random numbers)
    min_requirements = {
        'protein': 50,
        'vitamin': 60,
        'fat': 120,
        'carb': 30,
        'mineral': 40,
    }

    def check(self):
        healthy = False

        # Instead of checking the fields one by one,
        # use a loop over _fields.
        for field in self._fields:
            value = getattr(self, field)
            expected = self.min_requirements[field]
            if value < expected:
                print('{} is low!'.format(field.capitalize()))
                print('Required amount is {}'.format(expected))
                healthy = False

        if healthy:
            print('You are healthy')

示例用法：

n = Nutrition(
    protein=int(input('Enter Protein: ')),
    vitamin=int(input('Enter Vitamin: ')),
    fat=int(input('Enter Fat: ')),
    carb=int(input('Enter Carbs: ')),
    mineral=int(input('Enter Mineral: ')),
)

n.check()

这样做的好处是，如果您想要添加/删除一个字段，这是一个微不足道的更改。此外，如果您想添加更复杂的条件(例如，检查最大值而不仅仅是最小值)，这也是一个微不足道的变化。

我使用namedtuple主要是为了缓解懒惰。这有一个副作用，即您的字段是只读的，但即使没有namedtuple，您也可以简单地获得相同的结果。