ipaddress.IPv6Interface.ip drops the IPv6 scope ID

[augusto-rehfeldt]

Bug report

Bug description:

Documented behaviour: The ipaddress documentation, under IPv6Interface, says it implements the same attributes as IPv4Interface; the documented ip attribute is “An IPv4Address object with the address of the interface.” For IPv6Interface this is an IPv6Address object.

Expected: IPv6Address('fe80::1%eth0'), with scope_id 'eth0'

Actual: IPv6Address('fe80::1'), with scope_id None

import ipaddress as ip

s = 'fe80::1%eth0/0'
try:
    a, p = s.rsplit('/', 1)
    expected = ip.IPv6Address(a)
    if not 0 <= int(p) <= 128 or not expected.scope_id:
        raise ValueError('invalid prefix or missing scope')
    actual = ip.IPv6Interface(s).ip
    if actual != expected or actual.scope_id != expected.scope_id:
        print(f'REFUTATION CONFIRMED: {s!r} actual: {actual!r} expected: {expected!r}')
    else:
        print('REFUTATION REJECTED: actual matches the scoped address')
except ValueError as e:
    print(f'REFUTATION REJECTED: invalid input: {e}')

Output on Python 3.14.6 (Windows-11-10.0.26220-SP0), standard library ipaddress:

REFUTATION CONFIRMED: 'fe80::1%eth0/0' actual: IPv6Address('fe80::1') expected: IPv6Address('fe80::1%eth0')

This report was found and written by an automated property-testing tool I run (bugforge). The reproducer above was executed and its output is pasted unedited; no person reviewed the report before it was filed. The search script is in https://github.com/augusto-rehfeldt/bugforge-results/tree/main/ipaddress-20261003-050858-c2

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[ZeroIntensity]

See #158748 (comment).