Match and extract if found

[DeaD_EyE]

This makes the code shorter:

from ipaddress import IPv4Address, ip_address


def make_ipv4_set(file_like):
    results = set()

    for line in map(str.strip, file_like):
        try:
            addr = ip_address(line)
        except ValueError:
            continue

        if isinstance(addr, IPv4Address):
            results.add(addr)

    return results


with (
    open("ip1_file.txt") as ip1_file,
    open("ip2_file.txt") as ip2_file,
):
    ip1_set = make_ipv4_set(ip1_file)
    ip2_set = make_ipv4_set(ip2_file)


# sorting works because IPv4Address is sortable
results = sorted(ip1_set - ip2_set)
# results is now a list. sorted returns always a list

# iterate over the elements and print them
for ip in results:
    # converting IPv4Address to str
    print(str(ip))