I am new to Python, and I am trying to complete the following training problem:

=========

ATM machines allow 4 or 6 digit PIN codes and PIN codes cannot contain anything but exactly 4 digits or exactly 6 digits.

If the function is passed a valid PIN string, return true, else return false.

=========

My code is working for all the randomly generated pins except for: '12.0' '1234.0' '111-' '44444-'

def validate_pin(pin):
    numbers = '0123456789'
    if len(pin) != 4 and len(pin) != 6:
        return False
    else:
        for i in range(len(pin)):
            if pin[i] in numbers:
                return True
            else:
                break
        return False

Any idea why this would be? These characters do not live within my created variable.

I know there would be easier ways to do this same function. I would love to hear some of these, but also would love to learn why my current one does not work.

Thanks!

CodePudding user response：

As

Basically your code is checking if the first character is in numbers or not. If it is a number, the for loop breaks, if it isn't, the for loop breaks. Here's a small fix:

def validate_pin(pin):
numbers = '0123456789'
if len(pin) != 4 and len(pin) != 6:
    return False
else:
    for i in range(len(pin)):
        if pin[i] not in numbers:
            return False
        # if pin[i] in numbers:
        #     return True
        # else:
        #     break
    return True

CodePudding user response：

Your code is failing on these examples because it is only checking if the length is correct and if the first digit is a number.

This section of your code is where the issue is:

else:
        for i in range(len(pin)):
            if pin[i] in numbers:
                return True

In all of your test cases, i will initially be 0. It will check if pin[0] is in the set of numbers and return True. The return statement breaks you out of the loop and doesn't check pin[1], pin[2], etc. You need to change your code to check all digits.

CodePudding user response：

Good answers already - you break after the first character so other nonconforming ones are ignored. You could tighten up your code with

numbers = '0123456789'

def validate_pin(pin):
    return len(pin) in (4, 6) and all(n in numbers for n in pin)