Python script to minimize list of IPv4/IPv6 networks

collapse-subnets.py

#!/usr/bin/env python3

import ipaddress
import sys

source = []
result = []

for line in sys.stdin.readlines():
    source.extend(ipaddress.ip_network(net) for net in line.split())

src4 = []
src6 = []
for net in source:
    if net.version == 4:
        src4.append(net)
    else:
        src6.append(net)
result.extend(ipaddress.collapse_addresses(src4))
result.extend(ipaddress.collapse_addresses(src6))

sys.stderr.write('Collapsed {} networks into {}\n'.format(len(source), len(result)))

for net in result:
    sys.stdout.write('{}\n'.format(net))