Hi, I'm looking for feedback on issue 22941, "IPv4Interface arithmetic changes subnet mask".
As stated in the bug, I'd be happy to write a patch, if anyone would comment on my proposal. http://bugs.python.org/issue22941 Thank you, Søren Løvborg --- Addition and subtraction of integers are documented for ipaddress.IPv4Address and ipaddress.IPv6Address, but also work for IPv4Interface and IPv6Interface (though the only documentation of this is a brief mention that the Interface classes inherit from the respective Address classes). That's good. The problem is that adding/subtracting an integer to an Interface object changes the subnet mask (to max_prefixlen), something which is 1) not documented and 2) not the least surprising result. >>> import ipaddress >>> ipaddress.IPv4Interface('10.0.0.1/8') + 1 IPv4Interface('10.0.0.2/32') >>> ipaddress.IPv6Interface('fd00::1/64') + 1 IPv6Interface('fd00::2/128') Proposed behavior: >>> import ipaddress >>> ipaddress.IPv4Interface('10.0.0.1/8') + 1 IPv4Interface('10.0.0.2/8') >>> ipaddress.IPv6Interface('fd00::1/64') + 1 IPv6Interface('fd00::2/64') It all comes down to a judgment call: is this a bug, or expected (but undocumented) behavior? In PEP 387 lingo: Is this a "reasonable bug fix"? Or is it a "design mistake", thus calling for a FutureWarning first, and the actual change later? >>> ipaddress.IPv4Interface('1.2.3.4/16') + 1 __main__:1: FutureWarning: Arithmetic on IPv4Interface objects will change in Python 3.6. If you rely on the current behavior, change 'interface + n' to 'IPv4Interface(interface.ip + n, 32)' _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
