To run this:

• Install mitmproxy.
• Run the following command:

  $ mitmproxy --ignore '^(?!duckduckgo\.com)' -s proxy.py
  
• Test your proxy via configuring your browser or tools such as iptables (check the tutorial for more info), or you can test it out with curl:

  $ curl -x http://127.0.0.1:8080/ -k https://duckduckgo.com/