It’s not uncommon to expect CIDR notation vs an IP address in a script (e.g. one that’s being passed to another API. So the following script is an example of using the re module to identify if an entry is in CIDR or not (since it’s not always obvious how to go about doing so): The array can easily be changed or filled with a network mask or array of them rather than fixed as they are here – and the output could easily be to call another function rather than to just print output.