Ansible – How to use a variable in a variable name

Some times you have to construct the name of a variable to use it.

In previous versions of ansible there was a syntax like this one vars[ ansible_hostname + 'string' ]

Now, since the Ansible 2.5 you have another syntax very useful

- name: Show value of 'variablename'
  debug: msg="{{ lookup('vars', 'variabl' + myvar)}}"
  vars:
    variablename: hello
    myvar: ename

- name: Show default empty since i dont have 'variablnotename'
  debug: msg="{{ lookup('vars', 'variabl' + myvar, default='')}}"
  vars:
    variablename: hello
    myvar: notename

- name: Produce an error since i dont have 'variablnotename'
  debug: msg="{{ lookup('vars', 'variabl' + myvar)}}"
  ignore_errors: True
  vars:
    variablename: hello
    myvar: notename

- name: find several related variables
  debug: msg="{{ lookup('vars', 'ansible_play_hosts', 'ansible_play_batch', 'ansible_play_hosts_all') }}"

- name: alternate way to find some 'prefixed vars' in loop
  debug: msg="{{ lookup('vars', 'ansible_play_' + item) }}"
  loop:
    - hosts
    - batch
    - hosts_all

Find the documentaiton here