Read a file of network + CIDR masks, one per line; count the number of IP addresses it represents

countips.py

#!/usr/bin/env python3
#
# original: https://gist.github.com/joswr1ght/595d49d5a7914cf7305b73512f37186a

import sys

def countips(netblock):
    v = netblock.split('/')

    # nothing?
    if len(v) <= 0:
        return 0

    # no /subnet
    if len(v) == 1:
        v.append(32)

    _, cidr = v

    return 2**(32 - int(cidr))

if __name__ == '__main__':

    if len(sys.argv) != 2:
        print(f'Usage: {sys.argv[0]} <file with CIDR masks>')
        sys.exit(0)

    ipcount = 0

    with open(sys.argv[1]) as infile:
        for netblock in infile:
            ipcount += countips(netblock)

    print(ipcount)