cs50/sentimental/credit.py

#       American Express
# American Express uses 15-digit numbers
# starts with 34 or 37

#       MasterCard
# MasterCard uses 16-digit numbers
# starts with 51, 52, 53, 54, 55

#       Visa
# Visa uses 13- and 16-digit numbers
# starts with 4
# =======================================

# DEBUGGING NEEDED: problem with input

# credit card number
credit = 0

# input
inpt = input("Number: ")


def inptFunc(x):
    '''just a simple function for input automation'''
    try:
        int(x)
        return int(x)
    except ValueError:
        y = input("Number: ")
        inptFunc(y)


credit = inptFunc(inpt)

# calculate
while True:
    credit_str = str(credit)
    count = 0
    temp = 0

    # AmEx
    if len(credit_str) == 15 and credit_str[0] == '3':
        if credit_str[1] == '4' or '7':

            # 2nd to last digits
            length = len(credit_str) - 2

            # (1st step) make str
            temp_str = ""

            for i in credit_str:
                if length >= 0:
                    temp = int(credit_str[length]) * 2
                    temp_str += str(temp)

                    # increment index
                    length -= 2

            # (2nd step) add all of 'em
            for i in range(len(str(temp_str))):
                count += int(temp_str[i])

            # other digits
            length = len(credit_str) - 1

            for i in credit_str:
                if length >= 0:
                    count += int(credit_str[length])
                    length -= 2

            # check and out
            if count % 10 == 0:
                print("AMEX")
                break
            else:
                print("INVALID")
                break

    # MasterCard
    elif len(credit_str) == 16 and credit_str[0] == '5':
        if credit_str[1] == '1' or '2' or '3' or '4' or '5':

            # 2nd to last digits
            length = len(credit_str) - 2

            # (1st step) make str
            temp_str = ""

            for i in credit_str:
                if length >= 0:
                    temp = int(credit_str[length]) * 2
                    temp_str += str(temp)

                    # increment index
                    length -= 2

            # (2nd step) add all of 'em
            for i in range(len(str(temp_str))):
                count += int(temp_str[i])

            # other digits
            length = len(credit_str) - 1

            for i in credit_str:
                if length >= 0:
                    count += int(credit_str[length])
                    length -= 2

            # check and out
            if count % 10 == 0:
                print("MASTERCARD")
                break
            else:
                print("INVALID")
                break


# COPY-PASTE ramining: in Visa
    # Visa
    elif len(credit_str) == 13 or 16 and credit_str[0] == '4':

        # 2nd to last digits
        length = len(credit_str) - 2

        # (1st step) make str
        temp_str = ""

        for i in credit_str:
            if length >= 0:
                temp = int(credit_str[length]) * 2
                temp_str += str(temp)

                # increment index
                length -= 2

        # (2nd step) add all of 'em
        for i in range(len(str(temp_str))):
            count += int(temp_str[i])

        # other digits
        length = len(credit_str) - 1

        for i in credit_str:
            if length >= 0:
                count += int(credit_str[length])
                length -= 2

        # check and out
        if count % 10 == 0:
            print("VISA")
            break
        else:
            print("INVALID")
            break

    # if no cards matched
    else:
        print("INVALID")
        break