inventory.py

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import json
import socket
import subprocess


def main():
    print(json.dumps(inventory(), sort_keys=True, indent=2))


def inventory():
    ip_address = find_pi()

    return {
        'all': {
            'children': [
            'ungrouped' ]
        },
        'ungrouped':{
            'hosts':['local_mac']
        },
        '_meta': {
            'hostvars': {
                'local_mac': {
                    'ansible_host': ip_address,
                }
            },
        },
    }


def find_pi():
    for ip in all_local_ips():
        if port_22_is_open(ip):
            return ip


def all_local_ips():
    lines = subprocess.check_output(['arp', '-a']).split('\n')
    for line in lines:
        if '(' not in line:
            continue
        after_open_bracket = line.split('(')[1]
        ip = after_open_bracket.split(')')[0]
        yield ip


def port_22_is_open(ip):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    result = sock.connect_ex((ip, 22))
    return result == 0


if __name__ == '__main__':
    main()