67 lines
1.4 KiB
Python
67 lines
1.4 KiB
Python
from cs50 import get_string
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def invalid():
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print("INVALID")
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exit()
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# check luhn alghorythm
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def luhn_algo():
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nSum = 0
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isSecond = False
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# iterate over all card numbers from back
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for i in range(ndigits - 1, -1, -1):
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d = int(user_input[i])
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# check if number is every second
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if isSecond:
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d *= 2
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# check for double digit sums
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if d >= 10:
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nSum += int(d / 10)
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nSum += int(d % 10)
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else:
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nSum += d
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if isSecond:
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isSecond = False
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else:
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isSecond = True
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if nSum % 10 == 0:
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return True
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else:
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invalid()
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# check validity of card by using luhn alghoritm
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def card_check():
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beginning = int(user_input[0:2])
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if 39 < beginning < 50:
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if luhn_algo():
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print("VISA")
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elif beginning == 34 or beginning == 37:
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if luhn_algo():
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print("AMEX")
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elif 50 < beginning < 56:
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if luhn_algo():
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print("MASTERCARD")
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else:
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invalid()
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# takes user input and check if the value is positive number
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user_input = get_string("Enter credit card number:")
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try:
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if int(user_input) < 1:
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invalid()
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except:
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invalid()
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# calculates the length of input and if correct, continues with card_check
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ndigits = len(user_input)
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if ndigits == 15 or ndigits == 13 or ndigits == 16:
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card_check()
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else:
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invalid()
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