Ansible variables wildcard selection

Question

The only way I've found to select variables by a wildcard is to loop all variables and test match. For example

  tasks:
    - debug:
        var: item
      loop: "{{ query('dict', hostvars[inventory_hostname]) }}"
      when: item.key is match("^.*_python_.*$")

shell> ansible-playbook test.yml | grep key:
    key: ansible_python_interpreter
    key: ansible_python_version
    key: ansible_selinux_python_present

• Is there a more efficient way to do it?

Neither json_query([?key=='name']), nor lookup('vars', 'name') work with wildcards.

• Is there any other "wildcard-enabled" test, filter ...?

Note: regex_search is discussed in What is the syntax within the regex_search() to match against a variable?

Answer 1

You can select/reject with Jinja tests:

- debug:
    msg: "{{ lookup('vars', item) }}"
  loop: "{{ hostvars[inventory_hostname].keys() | select('match', '^.*_python_.*$') | list }}"

gives:

ok: [localhost] => (item=ansible_selinux_python_present) => {
    "msg": false
}
ok: [localhost] => (item=ansible_python_version) => {
    "msg": "2.7.10"
}

Answer 2

Update for Ansible 2.8 and higher versions.

There is the lookup plugin varnames added in Ansible 2.8. to "List of Python regex patterns to search for in variable names". See details

shell> ansible-doc -t lookup varnames

For example, to list the variables .*_python_.* the task below

    - debug:
        msg: "{{ item }}: {{ lookup('vars', item) }}"
      loop: "{{ query('varnames', '^.*_python_.*$') }}"

gives

TASK [debug] ***************************************************************
ok: [localhost] => (item=ansible_python_interpreter) => 
  msg: 'ansible_python_interpreter: /usr/bin/python3'
ok: [localhost] => (item=ansible_python_version) => 
  msg: 'ansible_python_version: 3.8.5'
ok: [localhost] => (item=ansible_selinux_python_present) => 
  msg: 'ansible_selinux_python_present: True

Moreover, the lookup plugin varnames will find also variables not 'instantiated' yet and therefore not included in the hostvars.