Ansible inventory script that uses /etc/hosts as it's data source

etc_hosts.py

#!/usr/bin/env python
# (c) 2015, Matt Martz <matt@sivel.net>
#
# This file is part of Ansible.
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

import sys
import json
import argparse


def etc_hosts():
    try:
        with open('/etc/hosts') as f:
            hosts_text = f.read()
    except Exception as e:
        raise SystemExit(e)

    hosts = {
        '_meta': {
            'hostvars': {}
        }
    }

    for line in hosts_text.splitlines():
        if not line.strip() or line.startswith('#'):
            continue

        names = line.split()
        ip = names.pop(0)
        for name in names:
            if name not in hosts:
                hosts[name] = {
                    'hosts': []
                }
            hosts[name]['hosts'].append(ip)
            if ip in ['127.0.0.1', '::1'] or name == 'localhost':
                hosts['_meta']['hostvars'][ip] = {
                    'ansible_connection': 'local',
                    'ansible_python_interpreter': sys.executable
                }
            else:
                hosts['_meta']['hostvars'][ip] = {}

    return json.dumps(hosts, indent=4, sort_keys=True)


def parse_args():
    parser = argparse.ArgumentParser()
    group = parser.add_mutually_exclusive_group(required=True)
    group.add_argument('--host', help='List details about a specific host')
    group.add_argument('--list', action='store_true', default=False,
                       help='List active servers')

    return parser.parse_args()


def main():
    args = parse_args()
    if args.host:
        sys.stderr.write('--host is not implemented')

    sys.stdout.write(etc_hosts())
    sys.exit(0)


if __name__ == '__main__':
    main()