How to loop over simple inventory on Ansible?

Question

I have the following Ansible inventory:

[UP]
u01
u02

I want print hostnames under the UP group and then store each hostname in a variable

I tried the following playbook with the command: ansible-playbook test_playbook.yml -i inventory

---
- name: Test
  hosts: localhost

  tasks: 
    - name: Show all the hosts in the inventory
      ansible.builtin.debug:
        msg: "{{ item }}"
      loop: "{{ groups['UP'] }}"
      register: result

I'm getting the following errors instead:

TASK [Show all the hosts in the inventory] *************************************
failed: [localhost] (item=u01) => {"ansible_loop_var": "item", "changed": false, "module_stderr": "", "module_stdout": "", "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error", "rc": 0, "item": "u01"}
failed: [localhost] (item=u02) => {"ansible_loop_var": "item", "changed": false, "module_stderr": "", "module_stdout": "", "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error", "rc": 0, "item": "u02"}

I can't seem to find the error to correct it, does anyone have any clue ?

Thank you!

Answer 1

---
- name: Test
  hosts: UP

  tasks: 
    - name: Show all the hosts in the inventory
      ansible.builtin.debug:
        msg: "{{ item }}"
      register: result
      delegate_to: localhost
      run_once: true
      with_inventory_hostnames:
        - UP