Error in ipaddress.address_exclude function

[out]

BPO	26457
Nosy	@ncoghlan, @serhiy-storchaka, @zhangyangyu
Files	address_exclude.patch: ipaddress._BaseNetwork.subnets include broadcast network

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2016-03-01.08:26:58.359>
created_at = <Date 2016-02-29.06:29:44.490>
labels = ['type-bug', 'library']
title = 'Error in ipaddress.address_exclude function'
updated_at = <Date 2016-03-01.08:26:58.359>
user = 'https://bugs.python.org/out'

bugs.python.org fields:

activity = <Date 2016-03-01.08:26:58.359>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2016-03-01.08:26:58.359>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2016-02-29.06:29:44.490>
creator = 'out'
dependencies = []
files = ['42054']
hgrepos = []
issue_num = 26457
keywords = ['patch']
message_count = 5.0
messages = ['260994', '261037', '261041', '261042', '261043']
nosy_count = 6.0
nosy_names = ['ncoghlan', 'pmoody', 'python-dev', 'serhiy.storchaka', 'xiang.zhang', 'out']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26457'
versions = ['Python 3.5', 'Python 3.6']

[out]

when i read in document 3.5.1,run the example in ipaddress.address_exclude function

>> n1 = ip_network('192.0.2.0/28')
>> n2 = ip_network('192.0.2.1/32')
>> list(n1.address_exclude(n2))

I got:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python 3.5\lib\ipaddress.py", line 794, in address_exclude
    s1, s2 = s1.subnets()
ValueError: not enough values to unpack (expected 2, got 1)

[zhangyangyu]

In old ipaddr.py, IPv4Network('192.0.2.0/31').subnet() returns [IPv4Network('192.0.2.0/32'), IPv4Network('192.0.2.1/32')], but ipaddress returns only [IPv4Network('192.0.2.0/32')].

It seems simply change end to end+1 in https://hg.python.org/cpython/file/tip/Lib/ipaddress.py#l921 can solve the problem and pass the test. But maybe there are some side effects.

[zhangyangyu]

I propose a patch simply add one to end so that the broadcast address network will appear in the result, which behaves the same as ipaddr.py. Corresponding tests are added. All tests are passed but I am afraid some logic may break.

[serhiy-storchaka]

LGTM. I have wrote similar patch but with different tests.

[python-dev]

New changeset 6d6c0a7b71f5 by Serhiy Storchaka in branch '3.5':
Issue bpo-26457: Fixed the subnets() methods in IP network classes for the case
https://hg.python.org/cpython/rev/6d6c0a7b71f5

New changeset c092148a1b55 by Serhiy Storchaka in branch 'default':
Issue bpo-26457: Fixed the subnets() methods in IP network classes for the case
https://hg.python.org/cpython/rev/c092148a1b55