Python: is this address a multicast address?

ismulticast.py

def ismulticast(hostname):
    """is this address a multicast address?"""
    # -- yes if bits 0-3 are 1110
    import socket
    import struct
    ip=socket.gethostbyname(hostname)
    mreq=struct.pack("4sl",socket.inet_aton(ip),socket.INADDR_ANY)
    return ord(mreq[0]) & 0xf0 == 0xe0


for i in ('localhost','138.72.131.168','239.239.239.7','10.1.1.1'):
    print ismulticast(i),i