Use with crankd turn off AirPort when on an Ethernet connection and turn AirPort back on when Ethernet disconnects

AirportKiller.py

#! /usr/bin/python

import syslog
import objc
from Foundation import NSAppleScript, CFPreferencesCopyAppValue,\
    CFPreferencesSetAppValue, CFPreferencesAppSynchronize
from SystemConfiguration import SCDynamicStoreCreate, SCDynamicStoreCopyValue

BUNDLE_ID = 'AirportKiller'

bundle_path = '/System/Library/Frameworks/CoreWLAN.framework'
objc.loadBundle('CoreWLAN', bundle_path=bundle_path, module_globals=globals())
iface = CWInterface.interface()
"""
Turn off wifi:
iface.setPower_error_(False, None)
Turn on wifi:
iface.setPower_error_(True, None)
"""


class LogHelper(object):
    def __init__(self, consoleOn=False, guiOn=False):
        self.console = consoleOn
        self.gui = guiOn
        self.msg = "AirportKiller: Network change detected"

    def add(self, txt):
        self.msg = self.msg + "\n" + txt

    def submit(self):
        if self.gui:
            self.aScriptNotify()
        if self.console:
            self.consoleLog()

    def consoleLog(self):
        syslog.syslog(syslog.LOG_ALERT, self.msg)

    def aScriptNotify(self):
        script = '''tell application "System Events"
            activate
            display dialog "{}" with title "AirPort Killer" buttons {{"OK"}}
        end tell
        '''.format(self.msg)
        s = NSAppleScript.alloc().initWithSource_(script)
        _ = s.executeAndReturnError_(None)


def dumpState(state):
    for key, val in state.items():
        CFPreferencesSetAppValue(key, val, BUNDLE_ID)
    CFPreferencesAppSynchronize(BUNDLE_ID)


def loadState():
    state = {}
    for key in ('AirportPower', 'AirportActive', 'EthernetActive'):
        state[key] = CFPreferencesCopyAppValue(key, BUNDLE_ID)
    return state


def getState():
    net_config = SCDynamicStoreCreate(None, "net", None, None)
    services = {}
    key = "Setup:/Network/Global/IPv4"
    service_uuids = SCDynamicStoreCopyValue(net_config, key)["ServiceOrder"]
    for uuid in service_uuids:
        key = "Setup:/Network/Service/{}/Interface".format(uuid)
        service = SCDynamicStoreCopyValue(net_config, key)
        if 'DeviceName' in service:
            services[service['DeviceName']] = service
    key = "State:/Network/Interface"
    interfaces = SCDynamicStoreCopyValue(net_config, key)['Interfaces']
    ether = {}
    for i in interfaces:
        # ignore devices not listed in network services
        if i not in services:
            continue
        # ignore bluetooth interfaces
        if i.startswith('awdl') or i.startswith('llw'):
            continue
        # ignore hidden interfaces like iPhone/iPad USB
        if services[i].get('HiddenConfiguration', False):
            continue
        key = "State:/Network/Interface/{}/Link".format(i)
        state = SCDynamicStoreCopyValue(net_config, key)
        key = "State:/Network/Interface/{}/AirPort".format(i)
        airport = SCDynamicStoreCopyValue(net_config, key)
        if airport:
            currentState = {'AirportPower': airport['Power Status'],
                            'AirportActive': state['Active']}
            continue
        if state:
            ether[i] = state['Active']
    currentState['EthernetActive'] = any(ether.values())
    return currentState


syslog.openlog(ident="AirportKiller", facility=syslog.LOG_DAEMON)
log = LogHelper(consoleOn=True, guiOn=False)
currentState = getState()
log.add("Current network state: {}".format(currentState))

try:
    previousState = loadState()
except:
    previousState = None

if previousState:
    log.add("Previous network state: {}".format(previousState))
else:
    log.add("Previous network state unknown.")
    if currentState['EthernetActive'] and currentState['AirportActive']:
        log.add("System docked, previous network state unknown. Killing"
                " Airport...")
        iface.setPower_error_(False, None)
    dumpState(getState())
    log.submit()
    quit()

if (previousState['EthernetActive'] and not currentState['EthernetActive'] and
        not currentState['AirportActive']):
    log.add("System undocked with AirPort off. Resurrecting AirPort...")
    iface.setPower_error_(True, None)
elif (not previousState['EthernetActive'] and currentState['EthernetActive']
        and currentState['AirportActive']):
    log.add("System docked with AirPort on. Killing AirPort...")
    iface.setPower_error_(False, None)
else:
    log.add("No actionable network changes.")

dumpState(getState())
log.submit()

com.googlecode.pymacadmin.crankd.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>SystemConfiguration</key>
	<dict>
		<key>State:/Network/Global/IPv4</key>
		<dict>
			<key>command</key>
			<string>/usr/bin/python '/usr/local/myorg/AirportKiller.py'</string>
		</dict>
	</dict>
</dict>
</plist>