[newswoop:F25:ansible (devel % u=)]$ cat pyver.yaml
---
- name: The first play
  hosts: localhost
  gather_facts: false
  tasks:
    - name: show ansible_python_interpreter
      debug:
        var: ansible_python_interpreter
[newswoop:F25:ansible (devel % u=)]$ python3.6 bin/ansible-playbook pyver.yaml
 [WARNING]: No inventory was parsed, only implicit localhost is available

 [WARNING]: provided hosts list is empty, only localhost is available


PLAY [The first play] ****************************************************************************

TASK [show ansible_python_interpreter] ***********************************************************
ok: [localhost] => {
    "ansible_python_interpreter": "/usr/bin/python3.6",
    "failed": false
}

PLAY RECAP ***************************************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0

[newswoop:F25:ansible (devel % u=)]$ python2.7 bin/ansible-playbook pyver.yaml
 [WARNING]: No inventory was parsed, only implicit localhost is available

 [WARNING]: provided hosts list is empty, only localhost is available


PLAY [The first play] ****************************************************************************

TASK [show ansible_python_interpreter] ***********************************************************
ok: [localhost] => {
    "ansible_python_interpreter": "/usr/bin/python2.7",
    "failed": false
}

PLAY RECAP ***************************************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0