How do I make a validation loop to make sure the user inputs the correct amount of times in a .split-CodePudding

This may be kind of stupid but I've made a really roundabout way of validating a credit card number. I'm still really new at python and coding in general and wanted to make it so that I can validate the amount of digits, whether or not the input is numbers, and to also make it so I can print the input split up like this: xxx-xxxx-xxxx

So far I have this (please excuse how messy and probably unnecessary a lot of it is!)

CreditOne = 0
CreditTwo = 0
CreditThree = 0

while True:
    CreditOne, CreditTwo, CreditThree = input("Enter the credit card number (separate with spaces): ").split()
    CreditCardList = [CreditOne, CreditTwo, CreditThree]
    CreditCardNumber = "-".join(CreditCardList)
    if CreditOne.isdigit() and CreditTwo.isdigit() and CreditThree.isdigit() and len(CreditOne) == 4 and len(CreditTwo) == 4 and len(CreditThree) == 4:
        break
    elif CreditOne == 0 or CreditTwo == 0 or CreditThree == 0:
        print("Please input a valid credit card number.")
        continue
    else:
        print("Please input a valid credit card number.")
        continue

print(CreditCardNumber)

It does the job for the most part except for the fact that if the user just inputs something like 4 4 or like a singular letter it will get a ValueError:

ValueError: not enough values to unpack (expected 3, got 1)

Basically what I've been trying to do is create a validation that allows the loop to continue after the error and return to the start of the loop. I've tried a try except loop and it didn't work, I wanted to get a second opinion on this and maybe some help from somebody who understands what I'm trying to achieve with my code.

CodePudding user response：

Another way you could do this is with exceptions - this will help you deal with other errors as well:

while True:
     try:
          CreditOne, CreditTwo, CreditThree = input("Enter the credit card number (separate with spaces): ").split()
         break
     except ValueError:
         print('Oops! That's not a valid number')

CodePudding user response：

Instead of unpacking first, then combining them into a list, do it the other way around:

CreditCardList = input("Enter the credit card number (separate with spaces): ").split()
if len(CreditCardList) == 3:
    CreditOne, CreditTwo, CreditThree = CreditCardList
    # ... do other stuff
else:
    print("You must enter exactly 3 numbers")

As a side note, study generator expressions, list comprehensions and built-ins such as all and any to further simplify your code. For example, the following line:

if CreditOne.isdigit() and CreditTwo.isdigit() and CreditThree.isdigit() and len(CreditOne) == 4 and len(CreditTwo) == 4 and len(CreditThree) == 4:

can be rewritten as

if all(c.isdigit() and len(c) == 4 for c in CreditCardList):