在python中使用循環來配置信用卡號

Question

我正在從事這個項目，我必須檢查信用卡號是否有效。 在這種情況下，我只需要一張8位數的信用卡（我知道那是不現實的）。 這是問題

信用卡號的最后一位數字是校驗位，它可以防止轉錄錯誤，例如一位數錯誤或兩位數轉換錯誤。 以下方法用於驗證實際的信用卡號，但為簡單起見，我們將用8位數字（而不是16位數字）來描述它。

•從最右邊的數字開始，形成每隔一個數字的總和。 例如，如果信用卡號為4358 9795 ，則得出的總和為5 + 7 + 8 + 3 = 23.

•將上一步中未包括的每個數字加倍。 將結果數字的所有數字相加。 例如，使用上面給出的數字，將數字加倍（從倒數第二個開始）， yields 18 18 10 8 。 將所有數字相加后得出1 + 8 + 1 + 8 + 1 + 0 + 8 = 27 。

•將前面兩個步驟的總和相加。 如果結果的最后一位為0，則該數字有效。 在我們的例子中，23 + 27 = 50，因此該數字有效。

編寫實現此算法的程序。 用戶應提供一個8位數字，並且您應該打印出該數字是否有效。 如果無效，則應打印將使其有效的校驗位的值。

我必須使用循環來做總和。 但是，我不知道該如何使用循環。

這是我的代碼

# Credit Card Number Check. The last digit of a credit card number is the check digit,
# which protects against transcription errors such as an error in a single digit or
# switching two digits. The following method is used to verify actual credit card
# numbers but, for simplicity, we will describe it for numbers with 8 digits instead
# of 16:
#     Starting from the rightmost digit, form the sum of every other digit. For
#     example, if the credit card number is 43589795, then you form the sum
#     5 + 7 + 8 + 3 = 23.
#    Double each of the digits that were not included in the preceding step. Add #    all
#     digits of the resulting numbers. For example, with the number given above,
#     doubling the digits, starting with the next-to-last one, yields 18 18 10 8. Adding
#     all digits in these values yields 1 + 8 + 1 + 8 + 1 + 0 + 8 = 27.
#     Add the sums of the two preceding steps. If the last digit of the result is 0, the
#     number is valid. In our case, 23 + 27 = 50, so the number is valid.
# Write a program that implements this algorithm. The user should supply an 8-digit
# number, and you should print out whether the number is valid or not. If it is not
# valid, you should print out the value of the check digit that would make the number
# valid.

    card_number = int(input("8-digit credit card number: "))

rights = 0
for i in card_number[1::2]:
   rights += int(i)

lefts = 0
for i in card_number[::2]:
   lefts += int(i)*2%10+int(i)*2/10

print card_number, (rights +lefts)/10

if remaining == 0:
    print("Card number is valid")

else:
    print("Card number is invalid")

    if digit_7 - remaining < 0:
        checkDigit = int(digit_7 + (10 - remaining))
        print("Check digit should have been:", checkDigit)

    else:
        checkDigit = int(digit_7 - remaining)
        print("Check digit should have been:", checkDigit)

Answer 1

如果我理解正確，那么您正在尋找這樣的東西：

cards = ["43589795"]
for card_number in cards:  
     rights = sum(map(int, card_number[1::2]))
     lefts = sum(map(lambda x: int(x)*2%10+int(x)*2/10, card_number[::2])) # sum of doubled values
     print card_number, (rights +lefts)/10

沒有地圖和lambda魔術的相同解決方案：

rights = 0
for i in card_number[1::2]:
   rights += int(i)

lefts = 0
for i in card_number[::2]:
   lefts += int(i)*2%10+int(i)*2/10

print card_number, (rights +lefts)/10

並完整回答您的問題：

card_number = str(raw_input("8-digit credit card number: ")).replace(" ", "")

rights = 0
for i in card_number[1::2]:
   rights += int(i)

lefts = 0
for i in card_number[::2]:
   lefts += int(i)*2%10+int(i)*2/10

remaining = (rights +lefts)%10

digit_7 = int(card_number[-1]) # Last digit

if remaining == 0:
    print("Card number is valid")

else:
    print("Card number is invalid")

    if digit_7 - remaining < 0:
        checkDigit = int(digit_7 + (10 - remaining))
        print("Check digit should have been:", checkDigit)

    else:
        checkDigit = int(digit_7 - remaining)
        print("Check digit should have been:", checkDigit)

Answer 2

這是使用numpy的解決方案：

import numpy as np
d1=np.transpose(np.array(list('43589795'), dtype=np.uint8).reshape((4,2)))[0]*2
d2=np.transpose(np.array(list('43589795'), dtype=np.uint8).reshape((4,2)))[1]
if (np.sum(np.hstack([list(entry) for entry in d1.astype(str)]).astype(np.uint8))+np.sum(d2))%10==0:
    return "Validated"

在示例情況下，我們得到了50個經過驗證的結果。

Answer 3

修剪信用卡號中的所有空格，然后嘗試以下代碼：

import itertools
sum = 0
for multiplicand,didgit in zip(itertools.cycle([2,1]), str(CREDIT_CARD_NUMBER)):
    result = multiplicand * int(didgit)
    sum += result / 10
    sum += result % 10
print "valid" if sum % 10 == 0 else "invalid"

上面的代碼遍歷信用卡號，並同時計算兩個總和。

Answer 4

這是另一種可能的解決方案：

cc_number = input("8-digit credit card number: ").replace(" ", "")
total1 = 0
total2 = 0

for digit in cc_number[-1::-2]:
    total1 += int(digit)

for digit in cc_number[-2::-2]:
    total2 += sum(int(x) for x in str(int(digit)*2))

remainder = (total1 + total2) % 10

if remainder == 0:
    print("Card is valid!")
else:
    invalid_check_digit = int(cc_number[-1])

    if invalid_check_digit - remainder < 0:
        valid_check_digit = invalid_check_digit + (10 - remainder)
    else:
        valid_check_digit = invalid_check_digit - remainder

    print("Card is invalid - the correct check digit is {}".format(valid_check_digit))  

提供以下輸出：

8-digit credit card number: 4358 9795
Card is valid!

要么：

8-digit credit card number: 4358 9794
Card is invalid - the correct check digit is 5