self.discipline()

host_modify.py

#!/usr/bin/env python3
import sys

number_of_args = len(sys.argv)
f = open("/etc/hosts", "a+")

for i in range(number_of_args - 1):
    f.write("127.0.0.1 %s\n" % sys.argv[i + 1])
    
# To use: 
# 1. Add this code to a file
# 2. Make executable: `chmod +x your-file-name`
# 3. Run as sudo and provide all sites you want to block
#    as space separated arguments
#    e.g. `sudo ./modify_hosts twitter.com facebook.com reddit.com`

# To disable:
# 1. Manually edit /etc/hosts and comment out the lines that include 
#    the hostnames you provided in the setup