Question

Using the above described algorithm, create a program that: (IN PYTHON)

1.Asks the user which type of credit card he/she would like to find the checksum for.

2. Based on the user's choice of credit card, asks the user for the n digits of the credit card. [Get the input as a string; it's easier to work with the string, so don't convert to an integer.]

3. Using the user's input of the n digits, finds the last digit of the sum.

4. Displays the resulting credit card i.e.; AMEX, MASTERCARD, VISA, or INVALID

According to Luhn’s algorithm, you can determine if a credit card number is (syntactically) valid as follows:

1. Multiply every other digit by 2, starting with the number’s second-to-last digit, and then add those products’ digits together.

2. Add the sum to the sum of the digits that weren’t multiplied by 2.

3. If the total’s last digit is 0 (or, put more formally, if the total modulo 10 is congruent to 0), the number is valid! That’s kind of confusing, so let’s try an example with American Express: 378282246310005

let’s first underline every other digit, starting with the number’s second-to-last digit: 378282246310005

let’s multiply each of the underlined digits by 2: 7*2 + 2*2 + 2*2 + 4*2 + 3*2 + 0*2 + 0*2

That gives us: 14 + 4 + 4 + 8 + 6 + 0 + 0 Now let’s add those products’ digits (i.e., not the products themselves) together: 1 + 4 + 4 + 4 + 8 + 6 + 0 + 0 = 27

Now let’s add that sum (27) to the sum of the digits that weren’t multiplied by 2: 27 + 3 + 8 + 8 + 2 + 6 + 1 + 0 + 5 = 60 Yup,

the last digit in that sum (60) is a 0, so the card is valid! So, validating credit card numbers isn’t hard, but it does get a bit tedious by hand.

Let’s write a program. Write a program that prompts the user for a credit card number and then reports whether it is a valid American Express, MasterCard, or Visa card number, per the definitions of each’s format herein.

your program’s last line of output be AMEX or MASTERCARD or VISA or DISCOVER or DINERS CLUB/CARTE BLANCHE or INVALID EXAMPLES Here are a few examples (user input is in bold):

Number: 378282246310005

AMEX

Number: 6175230925

INVALID

Answer 1

Screenshot

Program

#Function to find Digits Sum
def productSum(num):
    product=0
    list_of_ints = [int(i) for i in str(num)]
    for i in list_of_ints:
        product+=i
    return product
#Function to check validity of card
def isValid(creditCardNum):
    #Length check
    if(len(creditCardNum)!=15):
        return False
    else:
        sum=0
        #Odd index part calculation
        for i in range(1,len(creditCardNum),2):
            sum+=productSum(int(creditCardNum[i])*2)
        #Even index
        for i in range(0,len(creditCardNum),2):
            sum+=int(creditCardNum[i])
        #Validity check
        if(sum%10==0):
            return True
        else:
            return False
#Main function
def main():
    #Prompt for input
    num=input('Number: ')
    #Is valid then display which type
    if(isValid(num)):
        if(num[0]=='4'):
            print('VISA')
        elif(num[0]=='5'):
            print('MASTERCARD')
        elif(num[0]=='6'):
            print('DISCOVER')
        elif(num[0]=='3'):
            if(num[1]=='4'or num[1]=='7'):
                print('AMEX')
            if(num[1]=='0'or num[1]=='6'or num[1]=='8'):
                print('DINERS CLUB/CARTE BLANCHE')
        else:
            print('INVALID')
     #Otherwise Invalid
    else:
        print('INVALID')
if __name__=='__main__':
    main()

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Output

Number: 378282246310005
AMEX