IP string manipulation problem

[perfringo]

Thank you a lot!
Really apreciated!

You are welcome

If your source data is 'clean' and therefore there is no need to be 'defensive' it is possible to get same result without using ipaddress module (in first iteration it was used as convenient way to determine whether string is IPv4 or not). If all strings are guaranteed to be valid addresses or ranges containing '-' code can be simplified: moving getting addresses in range to separate function (how it's done) and using simple if clause (what is done):

def ip_from_range(ip_range):
    """Return list of ip addresses in ip_range.

    Separate ip addresses on '-', get value after last '.',
    convert to int and assign to names  first, last.

    Separate ip addresses on '-', get first address, get index
    of '.' from right, construct slice from address, get string
    consisting ip address first three groups (without comma) and
    assign to  name triplet.

    With list comprehension create list of ip addresses in range
    from first to last by joining triplet and range values.

    :param ip_range: first and last ip address separated by '-'
    :type ip_range: str
    :return: list of ip addresses in range
    :rtype: list
    """
    first, last = [int(el.split('.')[-1]) for el in ip_range.split('-')]
    triplet = addr[:ip_range.split('-')[0].rindex('.')]
    return [f'{triplet}.{i}' for i in range(first, last + 1)]

Now the code can be written:

new = []

for addr in addresses:
    if '-' in addr:
        new.extend(ip_from_range(addr))
    else:
        new.append(addr)