import re

from filelock import FileLock


try:
     import nltk

     __magic_name__    		=True
except (ImportError, ModuleNotFoundError):
     __magic_name__    		=False

if NLTK_AVAILABLE:
     with FileLock('''.lock''') as lock:
          nltk.download('''punkt''', quiet=True)







def 			__UpperCamelCase     (    A				):
     re.sub('''<n>'''			,				''''''			,				lowerCAmelCase__				)  # remove pegasus newline char
     assert NLTK_AVAILABLE, "nltk must be installed to separate newlines between sentences. (pip install nltk)"
     return "\n".join(nltk.sent_tokenize(lowerCAmelCase__				)				)






'''simple docstring'''

def 							_UpperCamelCase				(   lowerCAmelCase__:					str   )      -> bool:
							return credit_card_number.startswith(('34', '35', '37', '4', '5', '6')   )




def 							_UpperCamelCase				(   lowerCAmelCase__:					str   )      -> bool:
							SCREAMING_SNAKE_CASE_				=				credit_card_number
							SCREAMING_SNAKE_CASE_				=				0
							SCREAMING_SNAKE_CASE_				=				len(lowerCAmelCase__   ) - 2
							for i in range(lowerCAmelCase__		,-1		,-2   ):
														#  double the value of every second digit
														SCREAMING_SNAKE_CASE_				=				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
														SCREAMING_SNAKE_CASE_				=				cc_number[:i] + str(lowerCAmelCase__   ) + cc_number[i + 1 :]
														total += digit

							# Sum up the remaining digits
							for i in range(len(lowerCAmelCase__   ) - 1		,-1		,-2   ):
														total += int(cc_number[i]   )

							return total % 10 == 0




def 							_UpperCamelCase				(   lowerCAmelCase__:					str   )      -> bool:
							SCREAMING_SNAKE_CASE_				=				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(lowerCAmelCase__   ) <= 16:
														print(F"""{error_message} of its length."""   )
														return False

							if not validate_initial_digits(lowerCAmelCase__   ):
														print(F"""{error_message} of its first two digits."""   )
														return False

							if not luhn_validation(lowerCAmelCase__   ):
														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")





