How do I validate the format of a MAC address?

Question

What\'s the best way to validate that an MAC address entered by the user?

The format is HH:HH:HH:HH:HH:HH, where each H is a hexadecimal ch

Answer 1

Dash-separated MAC addresses can also contain a '01-' prefix, which specifies it is an Ethernet MAC address (not token ring, for example ... who uses token ring?).

Here's something that is somewhat complete and easy to read in a logical step-through way:

def IsMac(S):
  digits = S.split(':')
  if len(digits) == 1:
    digits = S.split('-')
    if len(digits) == 7:
      if digits[0] != '01':
        return False
      digits.pop(0)
  if len(digits) != 6:
    return False
  for digit in digits:
    if len(digit) != 2:
      return False
    try:
      int(digit, 16)
    except ValueError:
      return False
  return True


for test in ('01-07-09-07-b4-ff-a7',  # True
                '07:09:07:b4:ff:a7',  # True
                '07-09-07-b4-GG-a7',  # False
                 '7-9-7-b4-F-a7',     # False
                 '7-9-7-b4-0xF-a7'):  # False
  print test, IsMac(test)