Normalize MAC Address

mac=str('aA00CcA9e7Ff')
maclen=len(mac)
if maclen == 12:
    maclist=list(mac)

    positions=2,5,8,11,14

    for i in positions:
        maclist.insert(i,':')

    newmac=",".join(maclist)

    final12mac=newmac.replace(',','').lower()

    print final12mac

elif maclen == 17:
    mac17final=mac.replace('-',':').lower()
    print mac17final
else:
    print "There are only %s characters" % (maclen)