Question

Credit Cards

Credit card numbers follow patterns.

1. Cards must have 13 - 16 digits (inclusive)
2. Card numbers must start with the number(s):
   • 4 for Visa cards
   • 5 for MasterCard cards
   • 37 for American Express cards
   • 6 for Discover cards

Given that a number has satisfied the above criteria A and B the following steps are taken to validate the number:

1. Double every second digit from right to left.  If doubling the digit results in a two-digit number, add the two digits to get a single digit number
2. Add all of the single digit numbers from step 1 above
3. Add all of the digits in the odd places from right to left in the card number
4. Sum the results from steps 2 and 3 above
5. If the result from step 4 is evenly divisible by 10 the card number is valid.

Given the number:

4388576018402626

The steps 1 - 5 above would be (after determining that A an B above have been satisfied):

Step 1:

2 * 2 = 4

2 * 2 = 4

4 * 2 = 8

1 * 2 = 2

6 * 2 = 12 ( 1 + 2 = 3)

5 * 2 = 10 (1 + 0 = 1)

8 * 2 = 16 (1 + 6 = 7)

4 * 2 = 8

Step 2:

4 + 4 + 8 + 2 + 3 + 1 + 7 + 8 = 37

Step 3:

6 + 6 + 0 + 8 + 0 + 7 + 8 + 3 = 38

Step 4:

37 + 38 = 75

Step 5:

75 % 10

You are to write a program that will prompt the user to enter a card number.  You are then to determine if the number entered is valid or not.  You are then to print to the screen if the number entered is a valid credit card number or not.

Your are to complete this program using functions. You are to have a function main in which you will only call the functions you have developed.  The last line of your code is to be a call to main as below:

main()

Here are some valid numbers for testing purposes:

American Express	378282246310005
American Express	371449635398431
Discover	6011111111111117
Discover	6011000990139424
MasterCard	5555555555554444
MasterCard	5105105105105100
Visa	4111111111111111
Visa	4012888888881881
Visa	4222222222222

Done in Python Format please

Answer 1

Solution ::

The solution for the above question is given below with the screenshot of output.

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I have kept the logic simple and output as per the question.

I have used to numbers given in question:

• American Express 378282246310005
• American Express 371449635398431
• Discover 6011111111111117
• Discover 6011000990139424
• MasterCard 5555555555554444
• MasterCard 5105105105105100
• Visa 4111111111111111
• Visa 4012888888881881
• Visa 4222222222222

If there is anything else do let me know in comments

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--------------- CODE TO COPY -----------------------------------------------------------------------

def main():
  # user will input the credit card number as a string
  # call the function isValid() and print whether the credit card number is
  # valid or not valid
  
  num = input("Enter how many number you want to check ?")
  
  for i in range( 0 , int(num) ):
    
    card_no = input("\nEnter a credit card number as a long integer: ")
    
    if ( isValid( card_no )):
      print( str(card_no) + " is valid.")
    else:
      print( str(card_no) + " is invalid.")
  

def isValid(number) -> bool:
  # Return true if the card number is valid
  # hint you will have to call function sumOfDoubleEvenPlace() and sumOfOddPlace
  
  # It must have between 13 and 16 digits
  if ( len(number) < 13 or  len(number) > 16  ):
    return False
    
  # It must startswith 4,5,6 0r 37
  if ( ( number.startswith("4") == False) and ( number.startswith("5") == False) and ( number.startswith("6") == False) and ( number.startswith("37") == False) ):
    return False
  
  sum_of_even = sumOfDoubleEvenPlace(number)
  sum_of_odd  = sumOfOddPlace(number)
  
  sum_even_odd = sum_of_even + sum_of_odd
  
  if ( sum_even_odd %10 == 0 ):
    return True
    
  return False
  

def sumOfDoubleEvenPlace(number) -> int:
  # Get the result from Step 2
  
  result = 0 
  
  for i in range( len(number) - 2, -1 , -2):
    
    num = int ( number[i] ) * 2
    
    num = getDigit( num )
    
    result += num
  
  return result

def getDigit(number) -> int:
  # Return this number if it is a single digit, otherwise, return
  # the sum of the two digits
  if ( number > 9 ):
      number = int( str(number)[0] ) + int( str(number)[1] ) 
      
  return number

def sumOfOddPlace(number)-> int:
  # Return sum of odd place digits in number
  # Here are the two sample runs using the credit card numbers above:
  result = 0 
  
  for i in range( len(number) -1 , -1 , -2):
    
    num = int ( number[i] )
    result += num
    
  return result

print("Credit card number validation Program")
print()
main()

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Output :

Please rate my answer. Thank you..............