Example of an Ansible playbook that uses group_by

letsencrypt.yml

---
- hosts: all
  tasks:
    - group_by: key="{{ 'using_letsencrypt' if letsencrypt_certs|default([]) else 'not_using_letsencrypt' }}"
      changed_when: no
      tags: always

    - group_by: key="{{ ansible_distribution.lower() ~ '_' ~ ansible_distribution_release }}"
      changed_when: no
      tags: always

- hosts: using_letsencrypt:&ubuntu_xenial
  roles:
    - deadsnakes

- hosts: using_letsencrypt
  roles:
    - letsencrypt