convert between cidr and subnet

convert.py

import sys

def cidr_to_subnet(ip_cidr):
    """Convert IP/CIDR format to IP Subnet Mask format."""
    ip, cidr = ip_cidr.split('/')
    cidr = int(cidr)
    mask = ((1 << cidr) - 1) << (32 - cidr)
    subnet_mask = ".".join(str((mask >> i) & 0xff) for i in [24, 16, 8, 0])
    return "{} {}".format(ip, subnet_mask)

def subnet_to_cidr(ip_subnet):
    """Convert IP Subnet Mask format to IP/CIDR format."""
    ip, subnet = ip_subnet.split(None, 1)
    subnet_parts = map(int, subnet.split('.'))
    cidr = sum(bin(part).count('1') for part in subnet_parts)
    return "{}/{}".format(ip, cidr)