/24 subnet diversity for static proxies: what it is and how to check it

"""Count how many /24 subnets (and networks) your static exit IPs are spread over.

ips.txt: one exit IP per line (what api.ipify.org returns through each proxy).
Usage: python count_subnets.py ips.txt
"""
import ipaddress
import sys
from collections import Counter

path = sys.argv[1] if len(sys.argv) > 1 else "ips.txt"
with open(path, encoding="utf-8") as fh:
    ips = [ipaddress.IPv4Address(line.strip()) for line in fh if line.strip()]

per_24 = Counter(ipaddress.IPv4Network(str(ip) + "/24", strict=False) for ip in ips)
per_16 = Counter(ipaddress.IPv4Network(str(ip) + "/16", strict=False) for ip in ips)

print(len(ips), "IPs,", len(per_24), "distinct /24,", len(per_16), "distinct /16")
for net, count in per_24.most_common():
    share = 100 * count / len(ips)
    print("  %-18s %3d IPs  %5.1f%%" % (net, count, share))