import netifaces as nif

def mac_for_ip(ip):
  'Returns a list of MACs for interfaces that have given IP, returns None if not found'
  for i in nif.interfaces():
    addrs = nif.ifaddresses(i)
    try:
      if_mac = addrs[nif.AF_LINK][0]['addr']
      if_ip = addrs[nif.AF_INET][0]['addr']
    except IndexError, KeyError: #ignore ifaces that dont have MAC or IP
      if_mac = if_ip = None
    if if_ip == ip:
      return if_mac
  return None