How to filter list of IP addresses based on network in Ansible

Recent transition from ‘the ansible’ to ‘ansible-core + collections’ rendered documentation very fragmented. The problem I solved just now is following:

Given the list of IP addresses select only those belonging to a given network.

Example of input:

all_ipv4_addresses:
         - 188.42.54.219
         - 10.26.93.166
network: 10.0.0.0/8

Expected output:

["10.26.93.166"]

The solution

It’s in the docs, but, as I said, docs are fragmented and hard to find.

{{ all_ipv4_addresses | ansible.utils.reduce_on_network(network) }}

Output:

ok: [localhost] => {
    "msg": [
        "10.26.93.166"
    ]
}