def __new__(cls, x):
if not Luhn.verify(x):
raise ValueError('Luhn checksum failed')
if x < 10000000:
raise ValueError('Number too short')
if x > 9999999999999999999:
raise ValueError('Number too long')
return super(iso7812, cls).__new__(cls, x)
def check(n, x):
print (n, x)
assert Luhn.verify(n) == x
