Code for How to Validate Credit Card Numbers in Python Tutorial

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credit_card_validation.py

import argparse # Import argparse for command-line argument parsing import re # Import re for regular expression matching # Validate credit card number using Luhn Algorithm def luhn_algorithm(card_number): def digits_of(n): return [int(d) for d in str(n)] # Convert each character in the number to an integer digits = digits_of(card_number) # Get all digits of the card number odd_digits = digits[-1::-2] # Get digits from the right, skipping one digit each time (odd positions) even_digits = digits[-2::-2] # Get every second digit from the right (even positions) checksum = sum(odd_digits) # Sum all odd position digits for d in even_digits: checksum += sum(digits_of(d*2)) # Double each even position digit and sum the resulting digits return checksum % 10 == 0 # Return True if checksum modulo 10 is 0 # Function to check credit card number using Luhn's alogorithm def check_credit_card_number(card_number): card_number = card_number.replace(' ', '') # Remove spaces from the card number if not card_number.isdigit(): # Check if the card number contains only digits return False return luhn_algorithm(card_number) # Validate using the Luhn algorithm # Function to get the card type based on card number using RegEx def get_card_type(card_number): card_number = card_number.replace(' ', '') # Remove spaces from the card number card_types = { "Visa": r"^4[0-9]{12}(?:[0-9]{3})?$", # Visa: Starts with 4, length 13 or 16 "MasterCard": r"^5[1-5][0-9]{14}$", # MasterCard: Starts with 51-55, length 16 "American Express": r"^3[47][0-9]{13}$", # AmEx: Starts with 34 or 37, length 15 "Discover": r"^6(?:011|5[0-9]{2})[0-9]{12}$", # Discover: Starts with 6011 or 65, length 16 "JCB": r"^(?:2131|1800|35\d{3})\d{11}$", # JCB: Starts with 2131, 1800, or 35, length 15 or 16 "Diners Club": r"^3(?:0[0-5]|[68][0-9])[0-9]{11}$", # Diners Club: Starts with 300-305, 36, or 38, length 14 "Maestro": r"^(5018|5020|5038|56|57|58|6304|6759|676[1-3])\d{8,15}$", # Maestro: Various starting patterns, length 12-19 "Verve": r"^(506[01]|507[89]|6500)\d{12,15}$" # Verve: Starts with 5060, 5061, 5078, 5079, or 6500, length 16-19 } for card_type, pattern in card_types.items(): if re.match(pattern, card_number): # Check if card number matches the pattern return card_type return "Unknown" # Return Unknown if no pattern matches # Processing a file containing card numbers. def process_file(file_path): try: with open(file_path, 'r') as file: # Open the file for reading card_numbers = file.readlines() # Read all lines from the file results = {} for card_number in card_numbers: card_number = card_number.strip() # Remove any leading/trailing whitespace is_valid = check_credit_card_number(card_number) # Validate card number card_type = get_card_type(card_number) # Detect card type results[card_number] = (is_valid, card_type) # Store result return results except Exception as e: print(f"Error reading file: {e}") # Print error message if file cannot be read return None def main(): parser = argparse.ArgumentParser(description="Check if a credit card number is legitimate and identify its type using the Luhn algorithm.") parser.add_argument('-n', '--number', type=str, help="A single credit card number to validate.") # Argument for single card number parser.add_argument('-f', '--file', type=str, help="A file containing multiple credit card numbers to validate.") # Argument for file input args = parser.parse_args() # Parse command-line arguments if args.number: is_valid = check_credit_card_number(args.number) # Validate single card number card_type = get_card_type(args.number) # Detect card type print(f"[!] Credit card number {args.number} is {'valid' if is_valid else 'invalid'} and is of type {card_type}.") # Print result if args.file: results = process_file(args.file) # Process file with card numbers if results: for card_number, (is_valid, card_type) in results.items(): print(f"[!] Credit card number {card_number} is {'valid' if is_valid else 'invalid'} and is of type {card_type}.") # Print results for each card number # Execute tha main function if __name__ == '__main__': main()