Ansible: Fetch variable value from inventory file

Question

I am having issues fetching the value of ansible_user under rhel from the inventory file. Below are the few ways that I tried to fetch, everytime it says undefined rhel. Any suggestions as to how to retrieve it?

    - set_fact:
         SSHUSER: "{{  hostvars.[rhel].ansible_user }}"

    - set_fact:
         SSHUSER: "{{  rhel.ansible_user }}"

---
all:
  vars:
    project: test
  hosts:
  children:
    test_vm:
       hosts: 10.10.10.4
    example_vm:
       hosts: 10.10.10.5
    ubuntu:
      children:
        test_vm:
      vars:
        os: ubuntu
        ansible_user: "testuser"
    rhel:
      children:
        example_vm:
      vars:
        os: rhel
        ansible_user: "exampleuser"

Answer 1

The rhel you are referencing is a group, not a host -- a host may belong to multiple groups. The expression you'd want in order to achieve "the hostvars of some member of the group rhel" is the jinja2 expression: {{ hostvars[groups["rhel"][0]].ansible_user }}

Where groups["rhel"] are the list of strings of ansible inventory hostnames, and if one presumes they all have an equivalent ansible_user then it should be safe to just grab the first one, which is groups["rhel"][0] or the more verbose but perhaps clearer groups["rhel"]|first

Then, we want the hostvars for that host, not our own; since hostvars is a dict[str, dict] indexed by the ansible inventory hostname, we can plug that value into the hostvars dict as hostvars[groups["rhel"][0]] which is every hostvar, and then hostvars[groups["rhel"][0]].ansible_user gives back the ansible_user fact you requested