Get CIDR from network interfaces in Ohai.Loads ohai data in as JSON and returns the CIDR based on a device.

python-ohai-subprocess.py

import json
import subprocess

# Get Ohai Data
_ohai = subprocess.Popen(['ohai', '-l', 'fatal'], stdout=subprocess.PIPE)
ohai = _ohai.communicate()[0]
data = json.loads(ohai)

# Parse Ohai Data
def get_network(interface):
    device = data['network']['interfaces'].get(interface)
    if device is not None:
        if device.get('routes'):
            routes = device['routes']
            for net in routes:
                if 'scope' in net:
                    return net.get('destination', '127.0.0.0/8')
                    break
        else:
            return '127.0.0.0/8'
    else:
        return '127.0.0.0/8'

# Get the Subnet from the network interface
network = get_network(interface='eth2')