Object to sort IP addresses according to a best-match in an ip networks list

ipaddr_sorter.py

from ipaddr import IPv4Network, IPv4Address

"""
A module to sort ip addresses according to the best-match
in an ip networks list. If no matching network is found, ip
is sorted last.

example:

>>> networks = ['10.0.0.0/8', '172.16.0.0/12', '172.16.9.0/24']
>>> addrs = ['192.168.2.1', '10.4.5.6', '172.16.9.9', '10.2.3.4', '172.16.10.10']
>>> ipas = IPv4AddressSorter(networks)
>>> print([ip for ip in ipas.sorted(addrs)])
['10.4.5.6', '10.2.3.4', '172.16.10.10', '172.16.9.9', '192.168.2.1']

- the 10.x.x.x ips are first, because they match 10.0.0.0/8,
  their order amongst ips matching 10.0.0.0/8 is unchanged
- the 172.16.9.9 comes after 172.16.10.10 because it also matched
  172.16.9.0/24, which has a more-specific prefix (24 > 12)
- 192.168.2.1 comes last, because it matched nothing

you can choose the default position by putting a 0.0.0.0/0 entry in the list

"""

class IPv4AddressSorter(object):

    def __init__(self, networks):
        """
        :param net_order: list of networks
        """
        networks = [net if isinstance(net, IPv4Network) else IPv4Network(net)
                    for net in networks]
        self._networks = networks

    @property
    def networks(self):
        """
        :return: the list of networks used for sorting
        """
        for net in self._networks:
            yield str(net)

    def score(self, ip):
        """
        finds the sorting score for this address in the network table
        this is the key function to use in sort or sorted
        :param ip: the ip address to evaluate
        :return: an integer
        """
        prefixlen = 0
        sortidx = -1
        if not isinstance(ip, IPv4Address):
            ip = IPv4Address(ip)
        for idx, net in enumerate(reversed(self._networks)):
            if ip in net and idx > sortidx and net.prefixlen >= prefixlen:
                sortidx = idx
                prefixlen = net.prefixlen
        return -sortidx

    def sorted(self, ip_addresses):
        """
        :return: the ip_addresses in the list, in sorted order
        """
        return sorted(ip_addresses, key=self.score)