Question

我需要创建一个程序，该程序求2到100之间的偶数之和。我编写的部分如下：

def main():
    num = 2
    total = 0
    while num <= 100: 
        if num % 2 == 0:
            total = total + num
            num += 1
        else:
            num += 1
    print("Sum of even numbers between 2 and 100 is:", total)
main()

下一部分是我应该在当前的while循环中添加一个while循环，该循环要求输入Y / N，如果输入为yes，则将重复该程序。我花了很长时间尝试将以下内容放置在不同的位置：

while again == "Y" or again == "y":
again = input("Would you like to run this again? (Y/N)")

但是我无法使其正常工作，或者在最佳情况下，我无法获得它来打印数字的总和并询问是否要再次运行它，但是当我键入是时，它又回到询问我是否想要再次运行它。

我将另一个while语句放在哪里？

Answer 1

def sum_evens():
    active = True
    while active:
        sum_of_evens = 0
        for even in range(2, 101, 2):
            sum_of_evens += even
        print('Sum of the evens is:', sum_of_evens)
        while True:
            prompt = input('Type "Y" to start again or "N" to quit...\n')
            if prompt.lower() == 'y':  # doesn't matter if input is caps or not
                break
            elif prompt.lower() == 'n':
                active = False
                break
            else:
                print('You must input a valid option!')
                continue

sum_evens()

Answer 2

检查汇总是否为封闭形式总是很好的。该序列与sum of positive integers类似，它具有一个序列，因此没有理由遍历偶数。

def sum_even(stop):
    return (stop // 2) * (stop // 2 + 1)

print(sum_even(100)) # 2550

要将其置于while循环中，请在函数调用后要求用户输入并中断输入是否为'y'。

while True:
    stop = int(input('Sum even up to... '))
    print(sum_even(stop))
    if input('Type Y/y to run again? ').lower() != 'y':
        break

输出

Sum even up to... 100
2550
Type Y/y to run again? y
Sum even up to... 50
650
Type Y/y to run again? n

Answer 3

您应该在开头添加while循环，然后在末尾询问用户。像这样：

num = 2
total = 0
con_1 = True
while con_1:
   while num <= 100:
       if num % 2 == 0:
           total = total + num
           num += 1
       else:
           num += 1
   print("Sum of even numbers between 2 and 100 is:", total)
   ask = str(input("Do you want to run this program again(Y/n)?:"))
   if ask == "Y" or ask == "y":
       con_1 = True
   elif ask == "N" or ask == "n":
       con_1 = False
   else:
       print("Your input is out of bounds.")
       break

Answer 4

我的while循环要求再次运行程序，而不必在计算总和的循环内，那么以下应该回答您的约束：

def main():
    again = 'y'
    while again.lower() == 'y':
        num = 2
        total = 0
        while num <= 100:
            if num % 2 == 0:
                total = total + num
                num += 1
            else:
                num += 1
        print("Sum of even numbers between 2 and 100 is:", total)
        again = input("Do you want to run this program again[Y/n]?")

main()

请注意，如果您回答N（否，或者不是Y或y的其他内容），程序将停止。它不会永远问。

用户输入后重复while循环

4 个答案:

输出