如何循环回到Python中的开头

Question

我需要一些帮助来完成这段代码。 我一直在试图找出我的代码有什么问题。 我不知道如何使用 while 循环从顶部循环回来。 它也不会打印最后一位。 我得到了质数，但我不知道循环是如何工作的。 你能帮我吗？

while True:
    num=int(input("Enter a number:"))
    no="n"
    yes="y"
    
    if num >=1:
        for i in range(2, num):
            if (num % i) == 0:
                print(num,"is not a prime number")
                break
        else:
            print(num,"is a prime number")  
    x=str(input("If you want to continue press y, n if not:"))

if x==yes:
    print()
    #this part I don't know how to loop back to the start

elif x==no:        
        print("Okay")
    #and also the loop won't stop and print the text up there^^^ when I choose n

  
            

Answer 1

只将 if 放在 while 循环中，如果没有则跳出 while 循环

while True:
    ...
    x=str(input("If you want to continue press y, n if not:"))

    if x=="no":        
        print("Okay")
        break

Answer 2

如果您希望它无限重复，您的代码结构可能如下所示：

while True:  # The outer while loop, only ends when the player says "n"
    while True:
        # This is where you get the prime nums, paste the code for that here
    if x == "n":
        break  # This method will only stop the loop if the input is "no", else it keeps looping forever

或者，更简单地说，您可以在一个循环中执行此操作。 结构将是这样的：

while True:
    # Get if the num is prime, paste the code for that

    if x == "n":
        break

Answer 3

如果出现以下情况，可能的解决方案：

def is_prime(num):
    if num <= 1:
        return False
    if num % 2 == 0:
        return num == 2
    d = 3
    while d * d <= num and num % d != 0:
        d += 2
    return d * d > num
        

while True:
    num=int(input("Enter a number: "))
    
    if is_prime(num):
        print(f'{num} is a prime number')
    else:
        print(f'{num} is not a prime number')
        
    x = str(input("If you want to continue enter Y, or N if not: ")).lower()

    if x == 'y':
        print("let's start over...\n")

    elif x == 'n':      
        print("Okay, see you")
        break

退货：

Answer 4

您可以使用这样的代码。 在我看来 function 对于检查质数更有用。

def is_prime(x):
    for d in range(2, int(x**0.5)+1):
        if x % d == 0:
            return False
    return x > 1

no, yes = "n", "y"
x = yes
while x == yes:
    num=int(input("Enter a number:"))
    
    if is_prime(num):
        print(num,"is a prime number")
    else:
        print(num,"is not a prime number")

    x = input("If you want to continue press y, n if not:")

print("Okay")