如何将用户输入连接到 While 循环

Question

我正在编写一个代码，用户应该选择要吃的肉，然后随机分配其他食物来完成一顿饭。循环应该向您显示您拥有的物品，并且在循环结束时应该打印出总卡路里值。我编写了整个程序，但是当我提示用户吃肉时，它会停止并且不会进入 while 循环。这是程序：

import random

usermeal = []
meatcalories = 0
fruitcalories = 0
vegcalories = 0
desertcalories = 0

#defining a list of different foods...
meats = {"NY Strip": 300, "Shrimp": 100, "Lobster": 200, "Clams": 300, "Scallops": 200}
vegetables = {"Asparagus": 50, "Potato": 80, "Brocoli": 50, "Kale": 30, "Beans": 40}
fruits = {"Apple": 40, "Orange": 30, "Bananna":45, "Kiwi": 40, "Mango": 40}
deserts = {"Ice cream":300, "Brownie": 400, "Cookie": 200, "Chocolate":300, "Candy": 100}


print("We are going to make you a meal today. Each meal will have one item from each food category:")
print(meats)
print(vegetables)
print(fruits)
print(deserts)
print("Start by choosing one of the meats")
meatchoice = input("Please choose the meat that you want: ")


while len(usermeal) == 4:
    #prompt the user for their meat decision
    if meatchoice not in meats:
        print("Please choose a meat from the options!")
    meatchoice = input("Please choose the meat that you want: ")
    if meatchoice in meats:
        usermeal.append(meatchoice)
        meatcalories = meats.get(meatchoice)
        print("This is your meal so far", usermeal)

#randomly chooses a vegetable
    print("Now lets get the vegetable!")
    random_veg = random.choice(list(vegetables))
    print("The random vegetable is:", random_veg)
    usermeal.append(random_veg)
    vegcalories = vegetables.get(random_veg)
    print("This is your meal so far,", usermeal, "and its calorie count:", vegcalories)

#randomly chooses a fruit
    print("Now lets get the fruit!")
    random_fruit = random.choice(list(fruits))
    print("The random fruit is:", random_fruit)
    usermeal.append(random_fruit)
    fruitcalories = fruits.get(random_fruit)
    print("This is your meal so far,", usermeal, "and its calorie count:", fruitcalories)

#randomly chooses a desert
    print("Now lets get the desert!")
    random_desert = random.choice(list(deserts))
    print("The random desert is:", random_desert)
    usermeal.append(random_desert)
    desertcalories = deserts.get(random_desert)
    print("This is your meal so far,", usermeal, "and its calorie count:", desertcalories)

print("Now since we have all the foods, lets see how many calories it is")
totalcals = meatcalories + vegcalories + fruitcalories + desertcalories
print("Total Calorie Count: ", totalcals)

我不确定问题出在哪里。我知道它真的很小。如果有人可以向我指出，我将不胜感激。请显示代码中的更改。提前致谢！

Answer 1

看看你的while循环的条件是什么。

while len(usermeal) == 4:

现在在 while 循环运行之前，运行它并查看它的输出

print(len(usermeal))

TL;DR 是您运行 while 循环的条件在遇到它时不正确，因此循环永远不会运行。

Answer 2

import random

usermeal = []
meatcalories = 0
fruitcalories = 0
vegcalories = 0
desertcalories = 0

#defining a list of different foods...
meats = {"NY Strip": 300, "Shrimp": 100, "Lobster": 200, "Clams": 300, "Scallops": 200}
vegetables = {"Asparagus": 50, "Potato": 80, "Brocoli": 50, "Kale": 30, "Beans": 40}
fruits = {"Apple": 40, "Orange": 30, "Bananna":45, "Kiwi": 40, "Mango": 40}
deserts = {"Ice cream":300, "Brownie": 400, "Cookie": 200, "Chocolate":300, "Candy": 100}


print("We are going to make you a meal today. Each meal will have one item from each food category:")
print(meats)
print(vegetables)
print(fruits)
print(deserts)
print("Start by choosing one of the meats")
meatchoice = input("Please choose the meat that you want: ")


while len(usermeal) != 4:  #changed condition to NOT 4
    #prompt the user for their meat decision
    if meatchoice not in meats:
        print("Please choose a meat from the options!")
        meatchoice = input("Please choose the meat that you want: ")
    elif meatchoice in meats:  # also moved meatchoice within the if, and made this an elif
        usermeal.append(meatchoice)
        meatcalories = meats.get(meatchoice)
        print("This is your meal so far", usermeal)

#randomly chooses a vegetable
    print("Now lets get the vegetable!")
    random_veg = random.choice(list(vegetables))
    print("The random vegetable is:", random_veg)
    usermeal.append(random_veg)
    vegcalories = vegetables.get(random_veg)
    print("This is your meal so far,", usermeal, "and its calorie count:", vegcalories)

#randomly chooses a fruit
    print("Now lets get the fruit!")
    random_fruit = random.choice(list(fruits))
    print("The random fruit is:", random_fruit)
    usermeal.append(random_fruit)
    fruitcalories = fruits.get(random_fruit)
    print("This is your meal so far,", usermeal, "and its calorie count:", fruitcalories)

#randomly chooses a desert
    print("Now lets get the desert!")
    random_desert = random.choice(list(deserts))
    print("The random desert is:", random_desert)
    usermeal.append(random_desert)
    desertcalories = deserts.get(random_desert)
    print("This is your meal so far,", usermeal, "and its calorie count:", desertcalories)

print("Now since we have all the foods, lets see how many calories it is")
totalcals = meatcalories + vegcalories + fruitcalories + desertcalories
print("Total Calorie Count: ", totalcals)

我还认为您可以将随机选择的所有内容移到 while 之外，并且只循环选择肉类的条件。而且我认为您可以将条件更改为while meatchoice not in meats。但是，它按原样工作。

更新：

所以如果你想改变逻辑，它会是这样的：

import random

usermeal = []
meatcalories = 0
fruitcalories = 0
vegcalories = 0
desertcalories = 0

# defining a list of different foods...
meats = {"NY Strip": 300, "Shrimp": 100,
         "Lobster": 200, "Clams": 300, "Scallops": 200}
vegetables = {"Asparagus": 50, "Potato": 80,
              "Brocoli": 50, "Kale": 30, "Beans": 40}
fruits = {"Apple": 40, "Orange": 30, "Bananna": 45, "Kiwi": 40, "Mango": 40}
deserts = {"Ice cream": 300, "Brownie": 400,
           "Cookie": 200, "Chocolate": 300, "Candy": 100}


print("We are going to make you a meal today. Each meal will have one item from each food category:")
print(meats)
print(vegetables)
print(fruits)
print(deserts)
print("Start by choosing one of the meats")
meatchoice = input("Please choose the meat that you want: ")


while meatchoice not in meats:
    # prompt the user for their meat decision
    print("Please choose a meat from the options!")
    meatchoice = input("Please choose the meat that you want: ")

usermeal.append(meatchoice)
meatcalories = meats.get(meatchoice)
print("This is your meal so far", usermeal)

# randomly chooses a vegetable
print("Now lets get the vegetable!")
random_veg = random.choice(list(vegetables))
print("The random vegetable is:", random_veg)
usermeal.append(random_veg)
vegcalories = vegetables.get(random_veg)
print("This is your meal so far,", usermeal,
      "and its calorie count:", vegcalories)

# randomly chooses a fruit
print("Now lets get the fruit!")
random_fruit = random.choice(list(fruits))
print("The random fruit is:", random_fruit)
usermeal.append(random_fruit)
fruitcalories = fruits.get(random_fruit)
print("This is your meal so far,", usermeal,
      "and its calorie count:", fruitcalories)

# randomly chooses a desert
print("Now lets get the desert!")
random_desert = random.choice(list(deserts))
print("The random desert is:", random_desert)
usermeal.append(random_desert)
desertcalories = deserts.get(random_desert)
print("This is your meal so far,", usermeal,
      "and its calorie count:", desertcalories)

print("Now since we have all the foods, lets see how many calories it is")
totalcals = meatcalories + vegcalories + fruitcalories + desertcalories
print("Total Calorie Count: ", totalcals)