Bug report

Bug description:

While properties likeis_private account for IPv4-mapped IPv6 addresses, such as for example:

>>>ipaddress.ip_address("192.168.0.1").is_privateTrue>>>ipaddress.ip_address("::ffff:192.168.0.1").is_privateTrue

...the same doesn't currently apply to theis_loopback property:

>>>ipaddress.ip_address("127.0.0.1").is_loopbackTrue>>>ipaddress.ip_address("::ffff:127.0.0.1").is_loopbackFalse

At minimum, this inconsistency between different properties is counter-intuitive. Moreover,::ffff:127.0.0.0/104 is for all intents and purposes a loopback address, and should be treated as such.

For the record, this will now match the behavior of other languages such as Rust, Go and .NET, cf.rust-lang/rust#69772.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-117566: fix IPv6Address.is_loopback for IPv4-mapped loopbacks #117567
• [3.12] gh-117566: fix IPv6Address.is_loopback for IPv4-mapped loopbacks (GH-117567) #118391