cc-validate.py

#!/usr/bin/env python3

#Demo Python code for local meetup

#Imports the Python regular expression module
import re

#Function that checks if the first digit of the credit card number is good
def is_good_start_digit(my_cc):
  startdigit_pattern = r'^[4-6]'
  if re.match(startdigit_pattern, my_cc):
    return True
  else:
    return False

#Function that checks if the credit card number is the correct length, allowing for dashes
def is_good_cc_length(my_cc):
  alldigits_pattern = r'\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d\d'
  dash_pattern = r'\d\d\d\d-\d\d\d\d-\d\d\d\d-\d\d\d\d'
  if re.match(alldigits_pattern, my_cc):
    return True
  else:
    if re.match(dash_pattern, my_cc):
      return True
    else:
      return False

#Function that checks if the credit card number does not exceed the max allowed repeating digits (3)
def is_good_nonrepeating_digits(my_cc):
  repeat_pattern = r'(\d)\1{3}'
  my_cc_digits = re.sub('[^0-9]','', my_cc)
  if re.search(repeat_pattern, my_cc_digits):
    return False
  else:
    return True

#Main script execution segment
my_file = open('cc-list.txt', 'r')
cc_num = 0
cc_count = int(my_file.readline())
for cc_num in range(cc_num, cc_count):
  my_cc = my_file.readline()
  if is_good_start_digit(my_cc):
    if is_good_cc_length(my_cc):
      if is_good_nonrepeating_digits(my_cc):
        print("Valid")
      else:
        print("Invalid")
    else: 
      print("Invalid")
  else:
    print("Invalid")
my_file.close()