ansible - example of nasty custom jinja filter to get attribute from all hosts in a group

extras.py

# ansible_plugins/filter_plugins/extras.py
def getFromDict(dataDict, mapList):
    return reduce(lambda d, k: d[k], mapList, dataDict)

def get_host_attr_for_group(hosts, hostvars, keys):
    # given a list of nested keys, return the value for each host in hostvars
    results = []
    for host in hosts:
        results.append(getFromDict(hostvars[host], keys))
    return results

hosts

#vagrant ansible_ssh_port=2222 ansible_ssh_host=127.0.0.1

centos66 ansible_ssh_host=192.168.35.21 ansible_ssh_private_key=~/.vagrant/insecure_private_key
centos70 ansible_ssh_host=192.168.35.22 ansible_ssh_private_key=~/.vagrant/insecure_private_key
  
[centos]
centos66
centos70

output

TASK [debug msg=[u'6', u'7']] ***************************************************
ok: [localhost] => {
    "changed": false, 
    "msg": [
        "6", 
        "7"
    ]
}

play.yml

---
- hosts: centos
  remote_user: vagrant
  tasks:

- hosts: localhost
  remote_user: vagrant
  gather_facts: false
  vars:
    keys:
#      - ansible_default_ipv4
#      - address
      - ansible_distribution_major_version
  tasks:
    - debug: msg="{{ groups['centos'] | get_host_attr_for_group(hostvars, keys) }}"

What about groups['centos'] | map('extract', hostvars, 'ansible_distribution_major_version') | list? (Taken from Ansible's documentation https://docs.ansible.com/ansible/2.5/user_guide/playbooks_filters.html#extract-filter)

the extract filter didn't exist when I created this example