"String Index außerhalb des Bereichs Linie 7." Was ist falsch?

Question

Aufgabe: Berichte, ob der Benutzer eingegebene Kreditkartennummer ist:

VISA, Mastercard, AMEX oder INVALID

Amex: 15 Stellen - beginnt mit 34/37

Mastercard: 16 Digits - - beginnt mit 51/52/53/54/55

Visa: 13-16 Digits - beginnt mit 4

https://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm

Schnellnummer überprüfen mit: 378282246310005 "AMEX"

#Luhn algorithm to check credit card's number validity 
def Luhn (x, digits): 
    #Sum of every other number starting from before last n 
    sum1 = 0 
    i = 2 
    for i in range (digits): 
     digit = int(x[digits-i]) 
     if 2 * digit < 10: sum1 = sum1 + digit *2 
     else: sum1 = sum1 + 1 + (2 * digit -10) 
     i+=2 
    #Some of every other number starting from last n 
    sum2 = 0 
    i = 1 
    for i in range (digits): 
     digit = int(x[digits-i]) 
     sum2 = sum2 + digit 
     i+=2 
    #Some of both and condition return 
    if (sum1 + sum2) % 10 == 0: return True 
    else: return False 

def main(): 
    x = input("Insert your credit card's number for analysis\n") 
    # Length check 
    digits = len(x) 
    if digits <13 >16: 
     print("Invalid Length") 
     return 1 
    # Luhn algorithm check 
    check = Luhn(x, digits) 
    if check == False: 
     print("Invalid Card Number 'luhn'") 
     return 1 
    # Assigning letter id to first to numbers to determine card type 
    creditid1 = int(x[0]) 
    creditid2 = int(x[1]) 
    # Checking digits count and first to number to determine card type 
    if digits == 15 and creditid1 == 3 and (creditid2 == 4 or 7): 
     print("AMEX\n") 
    elif digits == 16 and creditid1 == 5 and (creditid2 == (1,6)): 
     print("MASTERCARD\n") 
    elif digits == 13 or 16 and creditid1 == 4: 
     print("VISA\n") 
    else: 
     print("Not Amex...\n Not Mastercard... \n Not Visa... \n") 

if __name__ == "__main__": 
    main() 

Answer 1

Zuerst i Null. Also x[digits-0] ist sicher außerhalb des Bereichs.

Ermöglicht die Schleife

for i in range (1,digits+1): 

auch zu

ändern, sollten Sie die Eingabe in str Typ konvertieren, bevor len() verwenden.

Modified Code

#Luhn algorithm to check credit card's number validity 
def Luhn (x, digits): 
    #Sum of every other number starting from before last n 
    sum1 = 0 
    i = 2 
    for i in range (1,digits+1): 
     digit = int(x[digits-i]) 
     if 2 * digit < 10: sum1 = sum1 + digit *2 
     else: sum1 = sum1 + 1 + (2 * digit -10) 
     i+=2 
    #Some of every other number starting from last n 
    sum2 = 0 
    i = 1 
    for i in range (1,digits+1): 
     digit = int(x[digits-i]) 
     sum2 = sum2 + digit 
     i+=2 
    #Some of both and condition return 
    if (sum1 + sum2) % 10 == 0: return True 
    else: return False 

def main(): 
    x = str(input("Insert your credit card's number for analysis\n")) 
    # Length check 
    digits = len(x) 
    if digits <13 >16: 
     print("Invalid Length") 
     return 1 
    # Luhn algorithm check 
    check = Luhn(x, digits) 
    if check == False: 
     print("Invalid Card Number 'luhn'") 
     return 1 
    # Assigning letter id to first to numbers to determine card type 
    creditid1 = int(x[0]) 
    creditid2 = int(x[1]) 
    # Checking digits count and first to number to determine card type 
    if digits == 15 and creditid1 == 3 and (creditid2 == 4 or 7): 
     print("AMEX\n") 
    elif digits == 16 and creditid1 == 5 and (creditid2 == (1,6)): 
     print("MASTERCARD\n") 
    elif digits == 13 or 16 and creditid1 == 4: 
     print("VISA\n") 
    else: 
     print("Not Amex...\n Not Mastercard... \n Not Visa... \n") 

if __name__ == "__main__": 
    main() 

Answer 2

Dies ist ein klassisches Off-by-one Fehler

ein zu dem Ergebnis hinzufügen

digit = int(x[digits-i]) 

Like this

digit = int(x[digits-i+1])