findvar filter plugin

example.log

PLAYBOOK: site.yml *******************************************************************************
1 plays in site.yml

PLAY [all] ***************************************************************************************
META: ran handlers

TASK [debug] *************************************************************************************
task path: /home/jtanner/workspace/issues/AP-HOSTVAR_LOOKUP/site.yml:5
ok: [el6host] => {
    "failed": false, 
    "msg": "YOU FOUND ME!"
}
ok: [testhost] => {
    "failed": false, 
    "msg": "YOU FOUND ME!"
}
ok: [el7host] => {
    "failed": false, 
    "msg": "YOU FOUND ME!"
}

TASK [debug] *************************************************************************************
task path: /home/jtanner/workspace/issues/AP-HOSTVAR_LOOKUP/site.yml:7
ok: [el7host] => {
    "failed": false, 
    "msg": "not found"
}
ok: [el6host] => {
    "failed": false, 
    "msg": "not found"
}
ok: [testhost] => {
    "failed": false, 
    "msg": "not found"
}

findvar.py

#!/usr/bin/env python

from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

from ansible.errors import AnsibleFilterError
from ansible.errors import AnsibleUndefinedVariable
from jinja2.runtime import Undefined


def var_find(vars, varname):
    """Iterate hosts and find the var"""
    for k, v in vars.items():
        for k2, v2 in v.items():
            if k2 == varname:
                return v2
    return Undefined()


class FilterModule(object):
    def filters(self):
        return {
            'findvar': var_find
        }

inventory.ini

el6host
el7host findme="YOU FOUND ME!"
testhost

site.yml

- hosts: all
  connection: local
  gather_facts: False
  tasks:
      - debug:
          msg: "{{ hostvars|findvar('findme') }}"
      - debug:
          msg: "{{ hostvars|findvar('badvarname')|default('not found') }}"