expand IOS-style vlan strings

vlan_unparser

def vlan_unparser(vlan_list_string):

    """
    Input: string in IOS-compressed VLAN syntax
    Output: list with ranges expanded
    """

    vlan_min = 1
    vlan_max = 4094

    result = []


    if re.match(r"^\d[\d\-,\s]+\d$", vlan_list_string):


        for num in re.findall(r"\D*(\d+)\D*", vlan_list_string):
            if int(num) not in range(vlan_min, vlan_max + 1):
                raise AnsibleFilterError(
                    "Invalid VLAN value found: {}".format(num)
                )

        elems = re.split(r"\s*,\s*", vlan_list_string)
        for elem in elems:
            if "-" in elem:
                pair = re.match(r"^\s*(\d+)\s*-\s*(\d+)\s*$", elem)
                if pair is not None:
                    start = int(pair.groups(0)[0])
                    end = int(pair.groups(0)[1])
                    result.extend(list(range(start, end + 1)))
                else:
                    raise AnsibleFilterError(
                        "Invalid VLAN range: {}".format(elem)
                    )
            else:
                result.append(int(elem))
    else:
        raise AnsibleFilterError(
            "Invalid VLAN range string: {}".format(vlan_list_string)
        )

    return sorted(result)