Question about Python recursive functions, What I did wrong?

Question

Things I want to achieve:

1. Login
2. Reset Password
3. Quit
What would you like to do? 2
Student ID: afrank
Error! Please enter your Student ID Number.
Student ID: 39211111x
Error! Please enter your Student ID Number.
Student ID: 39211111111
Error! Student ID Not Found
Student ID: 392111111
User Name: afrank
What year were you admitted? 2018
New Password: abc456
Confirm New Password: abc456
Password Changed!
1. Login
2. Reset Password
3. Quit
What would you like to do? 3

Codes:

def reset_password():

    isUser  = False
    changed = False

    sid = input('Student ID: ')
    try:
        sid = int(sid)
        import math
        digits = int(math.log10(sid)) + 1
        if digits != 9:
            print('Error: Student ID Not Found')
            reset_password()
        else:
            pass
    except:
        print('Error: Please enter your Student ID Number.')
        reset_password()

def options_menu():

    print('1. Login'+'\n'+'2. Reset Password'+'\n'+'3. Quit'+'\n'+'What would you like to do?')
    option = int(input())

    if option == 1:
        hello_login()
    elif option == 2:
        reset_password()
    elif option == 3:
        pass
options_menu()

Outputs:

1. Login
2. Reset Password
3. Quit
What would you like to do? 2
Student ID: afrank
Error! Please enter your Student ID Number.
Student ID: 39211111x
Error! Please enter your Student ID Number.
Student ID: 39211111111
Error! Student ID Not Found
Student ID: 392111111
User Name: afrank
What year were you admitted? 2018
New Password: abc456
Confirm New Password: abc456
Password Changed!
1. Login
2. Reset Password
3. Quit
What would you like to do? 3
Error! Please enter your Student ID Number
Error! Please enter your Student ID Number
Error! Please enter your Student ID Number
Process finished with exit code 0

I'm new to Python. I noticed the error repeated 3 times, which part did I do wrong in the recursive function?

yes, that's what I mean. Also, I don't see where your code asks for the year and new password. — Barmar
– Barmar, Commented Nov 19, 2019 at 4:29
@Barmar, this is part of the function codes. I think this is the part where I made a mistake. I didn't use recursive functions in the rest of the codes. So I didn't paste them here. Could you show me a while loop example based on my codes? Thank you! — Leo
– Leo, Commented Nov 19, 2019 at 4:32
You'll learn better if you try to write it yourself. Programming is not paint-by-numbers. — Barmar
– Barmar, Commented Nov 19, 2019 at 4:36

HelloWorld · Accepted Answer · 2019-11-19 04:35:34Z

2

Do not use such function calls to restart your function, recursion is not used in such a situation.

A recursive function has to fulfill an important condition to be used in a program: it has to terminate. A recursive function terminates, if with every recursive call the solution of the problem is downsized and moves towards a base case.

If you want to restart the reset_password function, simply use a while loop to wrap in the input validation part, break the loop when the input is valid.

Something like this will do.

def reset_password():

    done = False
    while not done:
        sid = input('Student ID: ')
        try:
            sid = int(sid)
            import math
            digits = int(math.log10(sid)) + 1
            if digits != 9:
                print('Error: Student ID Not Found')

            else:
                done = True
        except:
            print('Error: Please enter your Student ID Number.')

answered Nov 19, 2019 at 4:35

HelloWorld

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1 Comment

Leo Over a year ago

Thx bro, now I understand it better.

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