Nick Coghlan added the comment: As Stephen notes, the underlying problem appears to be a behavioural difference between two theoretically equivalent ways of defining a network:
>>> list(ipaddress.IPv4Network(('127.0.0.4', 31)).hosts()) [] >>> list(ipaddress.IPv4Network(('127.0.0.4/31')).hosts()) [IPv4Address('127.0.0.4'), IPv4Address('127.0.0.5')] Now, the first case is the documented behaviour: hosts() is *supposed to* exclude the network and broadcast address, and those are the only addresses in a /31. If you want to iterate over all the *addresses* in a network (including the network and broadcast addresses) then you need to iterate over the network object directly: >>> list(ipaddress.IPv4Network(('127.0.0.4', 31))) [IPv4Address('127.0.0.4'), IPv4Address('127.0.0.5')] >>> list(ipaddress.IPv4Network(('127.0.0.4/31'))) [IPv4Address('127.0.0.4'), IPv4Address('127.0.0.5')] However, as Emanuel found when writing his patch, there's currently an undocumented special case for /31 networks: the definition of "hosts" is *implicitly changed* for such instances to include the nominal network and broadcast address (by setting "self.hosts = self.__iter__"), presumably on the assumption that such networks represent a point-to-point link between two hosts, so the concepts of "network address" and "broadcast address" don't really apply. That special case seems pragmatically useful, so I think the right fix would be to: - document the special case that for /31 networks, hosts() includes the network and broadcast addresses (on the assumption the "network" is actually a point-to-point link between two hosts) - refactor IPv4Network.__init__ to first map the supplied input to a "candidate_address" and "candidate_netmask" and then use *common* validation logic to determine the actual network address and netmask (this will also address the "# fixme" comment for the int/bytes case) - check whether or not IPv6Network is affected by the same behavioural discrepancy ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue27683> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com