mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-27 23:11:09 +00:00
104 lines
3.4 KiB
Python
104 lines
3.4 KiB
Python
"""
|
||
Functions for testing the validity of credit card numbers.
|
||
|
||
https://en.wikipedia.org/wiki/Luhn_algorithm
|
||
"""
|
||
|
||
|
||
def validate_initial_digits(credit_card_number: str) -> bool:
|
||
"""
|
||
Function to validate initial digits of a given credit card number.
|
||
>>> valid = "4111111111111111 41111111111111 34 35 37 412345 523456 634567"
|
||
>>> all(validate_initial_digits(cc) for cc in valid.split())
|
||
True
|
||
>>> invalid = "14 25 76 32323 36111111111111"
|
||
>>> all(validate_initial_digits(cc) is False for cc in invalid.split())
|
||
True
|
||
"""
|
||
return credit_card_number.startswith(("34", "35", "37", "4", "5", "6"))
|
||
|
||
|
||
def luhn_validation(credit_card_number: str) -> bool:
|
||
"""
|
||
Function to luhn algorithm validation for a given credit card number.
|
||
>>> luhn_validation('4111111111111111')
|
||
True
|
||
>>> luhn_validation('36111111111111')
|
||
True
|
||
>>> luhn_validation('41111111111111')
|
||
False
|
||
"""
|
||
cc_number = credit_card_number
|
||
total = 0
|
||
half_len = len(cc_number) - 2
|
||
for i in range(half_len, -1, -2):
|
||
# double the value of every second digit
|
||
digit = int(cc_number[i])
|
||
digit *= 2
|
||
# If doubling of a number results in a two digit number
|
||
# i.e greater than 9(e.g., 6 × 2 = 12),
|
||
# then add the digits of the product (e.g., 12: 1 + 2 = 3, 15: 1 + 5 = 6),
|
||
# to get a single digit number.
|
||
if digit > 9:
|
||
digit %= 10
|
||
digit += 1
|
||
cc_number = cc_number[:i] + str(digit) + cc_number[i + 1 :]
|
||
total += digit
|
||
|
||
# Sum up the remaining digits
|
||
for i in range(len(cc_number) - 1, -1, -2):
|
||
total += int(cc_number[i])
|
||
|
||
return total % 10 == 0
|
||
|
||
|
||
def validate_credit_card_number(credit_card_number: str) -> bool:
|
||
"""
|
||
Function to validate the given credit card number.
|
||
>>> validate_credit_card_number('4111111111111111')
|
||
4111111111111111 is a valid credit card number.
|
||
True
|
||
>>> validate_credit_card_number('helloworld$')
|
||
helloworld$ is an invalid credit card number because it has nonnumerical characters.
|
||
False
|
||
>>> validate_credit_card_number('32323')
|
||
32323 is an invalid credit card number because of its length.
|
||
False
|
||
>>> validate_credit_card_number('32323323233232332323')
|
||
32323323233232332323 is an invalid credit card number because of its length.
|
||
False
|
||
>>> validate_credit_card_number('36111111111111')
|
||
36111111111111 is an invalid credit card number because of its first two digits.
|
||
False
|
||
>>> validate_credit_card_number('41111111111111')
|
||
41111111111111 is an invalid credit card number because it fails the Luhn check.
|
||
False
|
||
"""
|
||
error_message = f"{credit_card_number} is an invalid credit card number because"
|
||
if not credit_card_number.isdigit():
|
||
print(f"{error_message} it has nonnumerical characters.")
|
||
return False
|
||
|
||
if not 13 <= len(credit_card_number) <= 16:
|
||
print(f"{error_message} of its length.")
|
||
return False
|
||
|
||
if not validate_initial_digits(credit_card_number):
|
||
print(f"{error_message} of its first two digits.")
|
||
return False
|
||
|
||
if not luhn_validation(credit_card_number):
|
||
print(f"{error_message} it fails the Luhn check.")
|
||
return False
|
||
|
||
print(f"{credit_card_number} is a valid credit card number.")
|
||
return True
|
||
|
||
|
||
if __name__ == "__main__":
|
||
import doctest
|
||
|
||
doctest.testmod()
|
||
validate_credit_card_number("4111111111111111")
|
||
validate_credit_card_number("32323")
|