Question

I’m trying to make a Regular Expression that captures the following:
– XX or XX:XX, up to 6 repetitions (XX:XX:XX:XX:XX:XX), where X is a hexadecimal number.

In other words, I’m trying to capture MAC addresses than can range from 1 to 6 bytes.

regex = re.compile("^([0-9a-fA-F]{2})(?:(?:\:([0-9a-fA-F]{2})){0,5})$")

The problem is that if I enter for example “11:22:33”, it only captures the first match and the last, which results in [“11”, “22”].

The question: is there any method that {0,5} character will let me catch all repetitions, and not the last one?
Thanks!

Answer 1

Not in Python, no. But you can first check the correct format with your regex, and then simply split the string at ::

result = s.split(':')

Also note that you should always write regular expressions as raw strings (otherwise you get problems with escaping). And your outer non-capturing group does nothing.

---

Technically there is a way to do it with regex only, but the regex is quite horrible:

r"^([0-9a-fA-F]{2})(?:([0-9a-fA-F]{2}))?(?:([0-9a-fA-F]{2}))?(?:([0-9a-fA-F]{2}))?(?:([0-9a-fA-F]{2}))?(?:([0-9a-fA-F]{2}))?$"

But here you would always get six captures, just that some might be empty.