Ad blocker via /etc/hosts

block_hosts.py

#!/usr/bin/env python3

"""
Enable or disable ad blocker via /etc/hosts file
"""

import os
import sys
import shutil
import argparse
import requests
import subprocess


def main():
    parser = argparse.ArgumentParser(
        formatter_class=argparse.ArgumentDefaultsHelpFormatter
    )
    parser.add_argument("action", default="enable", choices=["enable", "disable"], nargs="?")
    args = parser.parse_args()

    if os.name == "nt":
        fn = r"c:\windows\system32\drivers\etc\hosts"
    else:
        fn = "/etc/hosts"

    link = "https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts"
    splitter = "#===ad-blocks"

    ad_hosts = requests.get(link).text
    etc_hosts = open(fn).read()
    local_hosts = etc_hosts.split(splitter, 1)[0].strip()

    if args.action == "disable":
        open(fn, "w").write("\n\n".join([local_hosts]) + "\n")
        print("Ad block disabled")
    else:
        open(fn, "w").write("\n\n".join([local_hosts, splitter, ad_hosts]) + "\n")
        print("Ad block enabled/updated")

    print("Attempting to flush DNS cache")
    output = ""
    if shutil.which("systemd-resolve"):
        output = subprocess.check_output([shutil.which("systemd-resolve"), "--flush-caches"])
    else:
        print("No known method of DNS cache flushing.")
    if output:
        print(output)


if __name__ == "__main__":
    main()