This is a stripped-down version of pklaus' python-inwx-xmlrpc. Nothing is added, there's just a lot removed and one of his examples renamed and slightly adapted (for use of IPv4).

1. Create a copy of the file python-inwx-xmlrpc.cfg.example called python-inwx-xmlrpc.cfg, and fill in your credentials and the domain. You can leave everything else as-is.
2. Start python3 inwx-dyndns.py as a service and give it the location of your IP address as an environment variable as IPv4_PATH.

I am forced to license this under the GPLv3. For details, see the file COPYING.