Loop from the start of the code until the user says stop in Python

Question

This is the question my teacher at school has given us:

Write a Python program to accept the value of an integer N and display all the factors of N. Repeat the above for multiple integers using a user-controlled loop.

I'm not having any trouble with the main part of the code, however i don't understand how to loop it properly so that the code runs through the beginning again till the user says N at the end when prompted.

This is my code:

#this is the main part of the code
def print_factors(x):
    print("The factors of",x,"are: ")
    for i in range(1,x+1):
        if x%i==0:
            print(i)

#this is the error handling part of the code
while True:
    try:
        n=int(input("Please enter a number: "))
    except ValueError:
        print("Please enter a valid number.")
        continue
    else:
        break
    
print_factors(n)
#this is the looping part where i am having trouble
N = input("Do you want to continue to find factors Y/N: ").upper()
while True:
    while N not in 'YN':
            if N == 'Y':
                print_factors(int(input("Enter a number: ")))
            elif N == 'N':
                break
            else:
                print("Invalid input, please try again.")
                N = input("Do you want to continue to find factors Y/N: ").upper()
                print_factors(int(input("Enter a number: ")))

I want the code to go back to the start and ask for input again, and then ask if the user wants to continue and so on. But when I got to the end, the loop shows these results:

Do you want to continue to find factors Y/N: e
Invalid input, please try again.
Do you want to continue to find factors Y/N: y
Enter a number: 42
The factors of 42 are: 
1
2
3
6
7
14
21
42

If I type something other than y, then it also works, and ends after looping only once. I want it to loop endlessly till the user gives the command to stop with a 'y' or 'Y' input and show an error message in all other cases.

Answer 1

I solve your problem by moving your inner while loop into the else case. Also, in the if statement N == 'Y' , I insert one more N = input(...) command:

N = input("Do you want to continue to find factors Y/N: ").upper()
while True:
    if N == 'Y':
        print_factors(int(input("Enter a number: ")))
        N = input("Do you want to continue to find factors Y/N: ").upper()
        
    elif N == 'N':
        break
    else:
        while N not in 'YN':
            print("Invalid input, please try again.")
            N = input("Do you want to continue to find factors Y/N: ").upper()

Result:

Please enter a number: 15
The factors of 15 are: 
1
3
5
15
Do you want to continue to find factors Y/N: y
Enter a number: 23
The factors of 23 are: 
1
23
Do you want to continue to find factors Y/N: e
Invalid input, please try again.
Do you want to continue to find factors Y/N: y
Enter a number: 32
The factors of 32 are: 
1
2
4
8
16
32
Do you want to continue to find factors Y/N: n
>>>

• Side note : running on Python 3.9.1, Window 10.
• Maybe you would want to include the same try-catch block into the user-controlled while loop.