tc_checksum.py

def tc_sum(i, k):
	return int(i)+int(k)

def tc_checksum(tc_no):
	if len(tc_no) < 11 or int(tc_no[10]) % 2 != 0 or int(tc_no[0]) == 0:
		return False
	single = reduce(tc_sum, [val for i, val in enumerate(tc_no[:9]) if i%2==0]) * 7
	double = reduce(tc_sum, [val for i, val in enumerate(tc_no[:8]) if i%2!=0])

	if not (single - double) % 10 == int(tc_no[9]):
		return False

	if not reduce(tc_sum, tc_no[:10]) % 10 == int(tc_no[10]):
		return False

	return True