---
- hosts: localhost
  gather_facts: no
  vars_files:
    - var_user.yml

  vars:
    field: firstname

  tasks:
    - name: 'user'
      debug:
        msg: '{{ user }}'

    - name: 'user["firstname"] '
      debug:
        msg: '{{ user["firstname"] }}'

    - name: 'user.firstname '
      debug:
        msg: '{{ user.firstname }}'

    - name: 'user[field]'
      debug:
        msg: '{{ user[field] }}'

    - name: 'user[field] mit Task-Var'
      debug:
        msg: '{{ user[field] }}'
      vars:
        field: lastname