Ansible: Get all the IP addresses of a group

I find the magic map extract here.

main_nodes_ips: "{{ groups['mainnodes'] | map('extract', hostvars, ['ansible_host']) | join(',') }}"
main_nodes_ips_with_port: "{{ groups['mainnodes'] | map('extract', hostvars, ['ansible_host']) | join(':3000,') }}:3000"

An alternative(idea comes from here):

main_nodes_ips: "{{ groups['mainnodes'] | map('extract', hostvars, ['ansible_eth0', 'ipv4', 'address']) | join(',') }}"

(Suppose the interface is eth0)

This do the trick for me. Not relying on the interface name

- main_nodes_ips: "{{ groups['mainnodes'] | map('extract', hostvars, ['ansible_default_ipv4', 'address']) | join(',') }}"

i came across this problem a while back and this is what i came up with (not optimal, but it works)

---
# playbook.yml
  - hosts: localhost
    connection: local

    tasks:
      - name: create deploy template
        template:
          src: iplist.txt
          dest: /tmp/iplist.txt
      - include_vars: /tmp/iplist.txt

      - debug: var=ip

and the template file is

ip:
{% for h in groups['webservers'] %}
 - {{ hostvars[h].ansible_ssh_host }}
{% endfor %}